#![allow(non_snake_case, unused_macros, unused_unsafe)]

use rustc_hash::FxHashMap as HashMap;
use rustc_hash::FxHashSet as HashSet;
use std::{
    cmp::Reverse,
    collections::BinaryHeap,
    fmt::{Debug, Display, Write},
    hash::Hash,
    mem::swap,
    ops::RangeInclusive,
    str::FromStr,
};

pub mod prelude {
    #[allow(unused_imports)]
    pub(crate) use super::{bits, dang, leek, mat, shucks, C};
    pub use super::{
        even, gcd, gt, l, lcm, lt, nail, pa, r, rand, reading, reading::Ext, sort, DigiCount, Dir,
        FilterBy, FilterBy3, GreekTools, IntoCombinations, IntoLines, IterͶ, NumTupleIterTools,
        ParseIter, Printable, Skip, TakeLine, TupleIterTools2, TupleIterTools2R, TupleIterTools3,
        TupleUtils, UnifiedTupleUtils, UnsoundUtilities, Widen, Ͷ, Α, Κ, Λ, Μ,
    };
    pub use rustc_hash::FxHashMap as HashMap;
    pub use rustc_hash::FxHashSet as HashSet;
    pub use std::{
        cmp::Ordering::*,
        cmp::{max, min},
        collections::{hash_map::Entry, VecDeque},
        fmt::{Debug, Display},
        hint::black_box as boxd,
        io::{self, Read, Write},
        iter,
        mem::{replace as rplc, swap, transmute as rint},
        ops::Range,
    };
}

macro_rules! C {
    ($obj:ident.$what:ident$($tt:tt)+) => {{
        let x = &mut $obj.$what;
        C!( x$($tt)+ )
    }};
    (&$buf:ident[$n:expr]) => {{
        #[allow(unused_unsafe)]
        unsafe {
            $buf.get_unchecked($n)
        }
    }};
    ($buf:ident[$n:expr]) => {{
        #[allow(unused_unsafe)]
        *unsafe {
            $buf.get_unchecked($n)
        }
    }};
    (&mut $buf:ident[$n:expr]) => {{
        #[allow(unused_unsafe)]
        unsafe {
            $buf.get_unchecked_mut($n)
        }
    }};
    ($buf:ident[$a:expr] = $rbuf:ident[$b:expr]) => {
        *unsafe { $buf.get_unchecked_mut($a) } = unsafe { *$rbuf.get_unchecked($b) }
    };
    ($buf:ident[$n:expr] = $e:expr) => {
        *unsafe { $buf.get_unchecked_mut($n) } = $e
    };
    ($buf:ident[$a:expr][$b:expr]) => {
        unsafe { *$buf.get_unchecked($a).get_unchecked($b) }
    };
    ($buf:ident[$a:expr][$b:expr] = $rbuf:ident[$ra:expr]) => {
        *unsafe { $buf.get_unchecked_mut($a).get_unchecked_mut($b) } =
            unsafe { *$rbuf.get_unchecked($ra) }
    };
    ($buf:ident[$a:expr][$b:expr] = $rbuf:ident[$ra:expr][$rb:expr]) => {
        *unsafe { $buf.get_unchecked_mut($a).get_unchecked_mut($b) } =
            unsafe { *$rbuf.get_unchecked($ra).get_unchecked($rb) }
    };
    ($buf:ident[$a:expr][$b:expr] = $c:expr) => {{
        #[allow(unused_unsafe)]
        {
            *unsafe { $buf.get_unchecked_mut($a).get_unchecked_mut($b) } = unsafe { $c }
        }
    }};
}
pub(crate) use C;

macro_rules! shucks {
    () => {
        if cfg!(debug_assertions) {
            unreachable!();
        } else {
            unsafe { std::hint::unreachable_unchecked() }
        }
    };
    ($fmt:literal $(, $args:expr)* $(,)?) => {
        if cfg!(debug_assertions) {
            unreachable!($fmt $(, $args)*);
        } else {
            unsafe { std::hint::unreachable_unchecked() }
        }
    };
    (if $x:expr) => {
        if $x {
            if cfg!(debug_assertions) {
                unreachable!();
            } else {
                unsafe { std::hint::unreachable_unchecked() }
            }
        }
    };
}
pub(crate) use shucks;

macro_rules! dang {
    () => {
        panic!()
    };
}
pub(crate) use dang;

macro_rules! leek {
    ($($allocation:ident)+) => {
        $(std::mem::forget($allocation);)+
    };
}
pub(crate) use leek;

macro_rules! mat {
    ($thing:ident { $($what:pat => $b:expr,)+ }) => {
        match $thing { $($what => { $b })+ _ => shucks!() }
    };
}
pub(crate) use mat;

#[cfg(target_feature = "avx2")]
unsafe fn count_avx<const N: usize>(hay: &[u8; N], needle: u8) -> usize {
    use std::arch::x86_64::*;
    let find = _mm256_set1_epi8(needle as i8);
    let mut counts = _mm256_setzero_si256();
    for i in 0..(N / 32) {
        counts = _mm256_sub_epi8(
            counts,
            _mm256_cmpeq_epi8(
                _mm256_loadu_si256(hay.as_ptr().add(i * 32) as *const _),
                find,
            ),
        );
    }
    const MASK: [u8; 64] = [
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
        255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
    ];
    counts = _mm256_sub_epi8(
        counts,
        _mm256_and_si256(
            _mm256_cmpeq_epi8(
                _mm256_loadu_si256(hay.as_ptr().add(N - 32) as *const _),
                find,
            ),
            _mm256_loadu_si256(MASK.as_ptr().add(N % 32) as *const _),
        ),
    );

    let sums = _mm256_sad_epu8(counts, _mm256_setzero_si256());
    (_mm256_extract_epi64(sums, 0)
        + _mm256_extract_epi64(sums, 1)
        + _mm256_extract_epi64(sums, 2)
        + _mm256_extract_epi64(sums, 3)) as usize
}

pub fn count<const N: usize>(hay: &[u8; N], what: u8) -> usize {
    #[cfg(target_feature = "avx2")]
    return unsafe { count_avx(hay, what) };
    #[cfg(not(target_feature = "avx2"))]
    hay.iter().filter(|&&x| x == what).count()
}

pub fn lcm(n: impl IntoIterator<Item = u64>) -> u64 {
    let mut x = n.into_iter();
    let mut lcm = x.by_ref().next().expect("cannot compute LCM of 0 numbers");
    let mut gcd;
    for x in x {
        gcd = crate::util::gcd(x, lcm);
        lcm = (lcm * x) / gcd;
    }
    lcm
}

#[repr(u8)]
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Ord, PartialOrd)]
pub enum Dir {
    N = b'U',
    E = b'R',
    S = b'D',
    W = b'L',
}

pub struct UnionFind {
    p: Vec<usize>,
    s: Vec<usize>,
}

impl UnionFind {
    pub fn new(size: usize) -> Self {
        Self {
            s: vec![1; size],
            p: (0..size).collect(),
        }
    }

    pub fn reset(&mut self) {
        self.s.fill(1);
        self.p
            .iter_mut()
            .enumerate()
            .for_each(|(idx, val)| *val = idx);
    }

    pub fn find(&mut self, key: usize) -> usize {
        if self.p[key] == key {
            return key;
        }
        let parent = self.find(self.p[key]);
        self.p[key] = parent;
        parent
    }

    pub fn union(&mut self, a: usize, b: usize) -> bool {
        let α = self.find(a);
        let β = self.find(b);
        if α == β {
            return false;
        }
        let a = self.s[α];
        let b = self.s[β];
        if a >= b {
            self.s[α] += b;
            self.p[β] = α;
        } else {
            self.s[β] += a;
            self.p[α] = β;
        }
        true
    }

    pub fn group_size(&self, group: usize) -> usize {
        self.s[group]
    }
}

pub trait UnsoundUtilities<T> {
    fn ψ(self) -> T;
}

impl<T> UnsoundUtilities<T> for Option<T> {
    #[cfg_attr(debug_assertions, track_caller)]
    fn ψ(self) -> T {
        if cfg!(debug_assertions) && self.is_none() {
            panic!();
        }
        unsafe { self.unwrap_unchecked() }
    }
}

impl<T, E> UnsoundUtilities<T> for Result<T, E> {
    #[cfg_attr(debug_assertions, track_caller)]
    fn ψ(self) -> T {
        if cfg!(debug_assertions) && self.is_err() {
            panic!();
        }
        unsafe { self.unwrap_unchecked() }
    }
}

pub struct LMap<K, V>(HashMap<K, V>, fn(&K) -> V)
where
    K: Eq + Hash + Clone;
impl<K: Ord + Eq + Debug + Hash + Clone, V: Copy + Debug> LMap<K, V> {
    pub fn new(f: fn(&K) -> V) -> Self {
        Self {
            0: HashMap::default(),
            1: f,
        }
    }

    pub fn with_cap(f: fn(&K) -> V, cap: usize) -> Self {
        Self {
            0: HashMap::with_capacity_and_hasher(cap, rustc_hash::FxBuildHasher::default()),
            1: f,
        }
    }

    pub fn get(&mut self, k: K) -> V {
        if let Some(x) = self.0.get(&k) {
            return *x;
        }
        // let mut ks = self.0.keys().collect::<Vec<_>>();
        // ks.sort();
        // println!("{ks:?}");
        let elm = self.1(&k);
        self.0.insert(k.clone(), elm);
        elm
    }
}

macro_rules! memoize {
    (|$pat:pat_param in $in:ty| -> $out:ty $body:block; $arg:expr) => {{
        static mut MEMOIZER: std::sync::OnceLock<crate::util::LMap<$in, $out>> =
            std::sync::OnceLock::new();
        unsafe {
            MEMOIZER.get_mut_or_init(|| crate::util::LMap::new(|$pat: &$in| -> $out { $body }))
        }
        .get($arg)
    }};
    (|$pat:pat_param in $in:ty| -> $out:ty $body:block; $arg:expr; with cap $cap:literal) => {{
        static mut MEMOIZER: std::sync::OnceLock<crate::util::LMap<$in, $out>> =
            std::sync::OnceLock::new();
        unsafe {
            MEMOIZER.get_mut_or_init(|| {
                crate::util::LMap::with_cap(|$pat: $in| -> $out { $body }, $cap)
            })
        }
        .get($arg)
    }};
}
#[allow(unused_imports)]
pub(crate) use memoize;

pub fn countg_with_check<N: Debug + PartialEq + Hash + Eq + Copy, I: Iterator<Item = N>>(
    start: N,
    graph: &mut impl Fn(N) -> I,
    ok: &mut impl Fn(N, N) -> bool,
    sum: &mut usize,
    end: &mut impl Fn(N) -> bool,
) {
    if end(start) {
        *sum += 1;
    } else {
        graph(start)
            .map(|x| {
                if ok(start, x) {
                    // println!("\"{start:?}\" -> \"{x:?}\"");
                    countg_with_check(x, graph, ok, sum, end);
                }
            })
            .Θ();
    }
}

pub fn countg_uniq_with_check<N: Debug + PartialEq + Hash + Eq + Copy, I: Iterator<Item = N>>(
    start: N,
    graph: &mut impl Fn(N) -> I,
    ok: &mut impl Fn(N, N) -> bool,
    sum: &mut usize,
    end: &mut impl Fn(N) -> bool,
    has: &mut HashSet<N>,
) {
    if end(start) && has.insert(start) {
        *sum += 1;
    } else {
        graph(start)
            .map(|x| {
                if ok(start, x) {
                    countg_uniq_with_check(x, graph, ok, sum, end, has);
                }
            })
            .Θ();
    }
}

pub fn countg<N: Debug + PartialEq + Hash + Eq + Copy, I: Iterator<Item = N>>(
    start: N,
    graph: &mut impl Fn(N) -> I,
    sum: &mut usize,
    end: &mut impl Fn(N) -> bool,
    has: &mut HashSet<N>,
) {
    if end(start) {
        *sum += 1;
    } else {
        graph(start)
            .map(|x| {
                if has.insert(x) {
                    countg(x, graph, sum, end, has);
                }
            })
            .Θ();
    }
}

// pub fn appearances(x: )

pub fn iterg<N: Debug + Copy, I: Iterator<Item = N>>(
    start: N,
    graph: &mut impl Fn(N) -> I,
    end: &mut impl Fn(N) -> bool,
    finally: &mut impl FnMut(N),
) {
    if end(start) {
        finally(start);
    } else {
        graph(start).map(|x| iterg(x, graph, end, finally)).Θ();
    };
}

pub fn show<N: Debug + Eq + Hash + Copy + Ord, I: Iterator<Item = (N, u16)>, D: Display>(
    graph: impl Fn(N) -> I,
    start: N,
    end: impl Fn(N) -> bool,
    name: impl Fn(N) -> D,
) {
    println!("digraph {{");
    let mut s = HashSet::default();
    let mut q = BinaryHeap::new();
    q.push(Reverse((0, start)));
    while let Some(Reverse((c, n))) = q.pop() {
        if end(n) {
            println!("}}");
            return;
        }
        if !s.insert(n) {
            continue;
        }
        print!("\t{}", name(n));
        for (n, d) in graph(n) {
            if s.contains(&n) {
                continue;
            }
            print!(" -> {}", name(n));
            q.push(Reverse((c + d, n)));
        }
        println!(";");
    }
    dang!();
}

pub fn dijkstra_h<N: Debug + Eq + Hash + Copy + Ord, I: Iterator<Item = (N, u16)>>(
    graph: impl Fn(N) -> I,
    start: N,
    end: impl Fn(N) -> bool,
    h: impl Fn(N) -> u16,
) -> u16 {
    let mut q = BinaryHeap::new();
    let mut s = HashSet::default();
    q.push(Reverse((h(start), 0, start)));
    while let Some(Reverse((_, c, n))) = q.pop() {
        if end(n) {
            return c;
        }
        if !s.insert(n) {
            continue;
        }
        for (n, d) in graph(n) {
            if s.contains(&n) {
                continue;
            }
            q.push(Reverse((h(n) + c + d, c + d, n)));
        }
    }
    dang!()
}

pub fn dijkstra<N: Debug + Eq + Hash + Copy + Ord, I: Iterator<Item = (N, u16)>>(
    graph: impl Fn(N) -> I,
    start: N,
    end: impl Fn(N) -> bool,
) -> Option<u16> {
    let mut q = BinaryHeap::new();
    let mut s = HashSet::default();
    q.push(Reverse((0, start)));
    while let Some(Reverse((c, n))) = q.pop() {
        if end(n) {
            return Some(c);
        }
        if !s.insert(n) {
            continue;
        }
        for (n, d) in graph(n) {
            if s.contains(&n) {
                continue;
            }
            // print!("{n:?} ");
            q.push(Reverse((c + d, n)));
        }
    }
    None
}

impl std::ops::Add<(i64, i64)> for Dir {
    type Output = (i64, i64);
    fn add(self, (x, y): (i64, i64)) -> Self::Output {
        match self {
            Dir::N => (x, y - 1),
            Dir::E => (x + 1, y),
            Dir::S => (x, y + 1),
            Dir::W => (x - 1, y),
        }
    }
}

impl std::ops::Add<(usize, usize)> for Dir {
    type Output = (usize, usize);
    fn add(self, (x, y): (usize, usize)) -> Self::Output {
        match self {
            Dir::N => (x, y.wrapping_sub(1)),
            Dir::E => (x.wrapping_add(1), y),
            Dir::S => (x, y.wrapping_add(1)),
            Dir::W => (x.wrapping_sub(1), y),
        }
    }
}

impl std::ops::Add<(i32, i32)> for Dir {
    type Output = (i32, i32);
    fn add(self, (x, y): (i32, i32)) -> Self::Output {
        match self {
            Dir::N => (x, y - 1),
            Dir::E => (x + 1, y),
            Dir::S => (x, y + 1),
            Dir::W => (x - 1, y),
        }
    }
}

impl std::ops::Add<(u16, u16)> for Dir {
    type Output = (u16, u16);

    fn add(self, (x, y): (u16, u16)) -> Self::Output {
        match self {
            Dir::N => (x, y - 1),
            Dir::E => (x + 1, y),
            Dir::S => (x, y + 1),
            Dir::W => (x - 1, y),
        }
    }
}

impl std::ops::Add<(i16, i16)> for Dir {
    type Output = (i16, i16);
    fn add(self, (x, y): (i16, i16)) -> Self::Output {
        match self {
            Dir::N => (x, y - 1),
            Dir::E => (x + 1, y),
            Dir::S => (x, y + 1),
            Dir::W => (x - 1, y),
        }
    }
}

impl std::ops::Add<(u8, u8)> for Dir {
    type Output = (u8, u8);

    fn add(self, (x, y): (u8, u8)) -> Self::Output {
        match self {
            Dir::N => (x, y.wrapping_sub(1)),
            Dir::E => (x.wrapping_add(1), y),
            Dir::S => (x, y.wrapping_add(1)),
            Dir::W => (x.wrapping_sub(1), y),
        }
    }
}

impl Dir {
    pub fn turn_90(self) -> Self {
        match self {
            Dir::N => Dir::E,
            Dir::E => Dir::S,
            Dir::S => Dir::W,
            Dir::W => Dir::N,
        }
    }
    pub fn turn_90ccw(self) -> Self {
        match self {
            Dir::N => Dir::W,
            Dir::E => Dir::N,
            Dir::S => Dir::E,
            Dir::W => Dir::S,
        }
    }
}

pub fn pa<T: std::fmt::Debug>(a: &[T]) {
    for e in a {
        print!("{e:?}");
    }
    println!();
}

pub fn gcd(mut a: u64, mut b: u64) -> u64 {
    if a == 0 || b == 0 {
        return a | b;
    }
    let shift = (a | b).trailing_zeros();
    a >>= shift;
    loop {
        b >>= b.trailing_zeros();
        if a > b {
            swap(&mut a, &mut b);
        }
        b -= a;
        if b == 0 {
            break;
        }
    }
    a << shift
}

pub trait Λ {
    fn λ<T: FromStr>(&self) -> T
    where
        <T as FromStr>::Err: std::fmt::Display;
}

impl Λ for String {
    fn λ<T: FromStr>(&self) -> T
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        self.as_str().λ()
    }
}
impl Λ for &[u8] {
    fn λ<T: FromStr>(&self) -> T
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        std::str::from_utf8(self).α().λ()
    }
}
impl Λ for &str {
    /// parse, unwrap
    fn λ<T: FromStr>(&self) -> T
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        match self.parse() {
            Ok(v) => v,
            Err(e) => {
                panic!(
                    "{e}: {self} should parse into {}",
                    std::any::type_name::<T>()
                )
            }
        }
    }
}
pub trait Κ {
    fn κ<T: FromStr>(self) -> impl Iterator<Item = T>
    where
        <T as FromStr>::Err: std::fmt::Display;
}

impl Κ for &[u8] {
    fn κ<T: FromStr>(self) -> impl Iterator<Item = T>
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        std::str::from_utf8(self).unwrap().κ()
    }
}

impl Κ for &str {
    fn κ<T: FromStr>(self) -> impl Iterator<Item = T>
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        self.split_ascii_whitespace().map(|x| x.λ())
    }
}

pub trait Α<T> {
    fn α(self) -> T;
}

impl<T, E: std::fmt::Display> Α<T> for Result<T, E> {
    #[cfg_attr(debug_assertions, track_caller)]
    fn α(self) -> T {
        match self {
            Ok(v) => v,
            Err(e) => {
                panic!("unwrap failed: {e}");
            }
        }
    }
}
impl<T> Α<T> for Option<T> {
    #[cfg_attr(debug_assertions, track_caller)]
    fn α(self) -> T {
        match self {
            Some(v) => v,
            None => panic!("nothingness!"),
        }
    }
}

pub trait DigiCount {
    fn ͱ(self) -> u32;
}

pub const powers: [u64; 20] = car::from_fn!(|x| 10u64.pow(x as u32));
// https://stackoverflow.com/a/9721570
impl DigiCount for u64 {
    fn ͱ(self) -> u32 {
        static powers: [u64; 20] = car::from_fn!(|x| 10u64.pow(x as u32));
        static mdigs: [u32; 65] = car::from_fn!(|x| 2u128.pow(x as u32).ilog10() + 1);
        let bit = std::mem::size_of::<Self>() * 8 - self.leading_zeros() as usize;
        let mut digs = mdigs[bit];
        if self < C! { powers[digs as usize - 1] } {
            digs -= 1;
        }
        digs
    }
}

impl DigiCount for u32 {
    fn ͱ(self) -> Self {
        static powers: [u32; 10] = car::from_fn!(|x| 10u32.pow(x as u32));
        static mdigs: [u32; 33] = car::from_fn!(|x| 2u128.pow(x as u32).ilog10() + 1);
        let bit = std::mem::size_of::<Self>() * 8 - self.leading_zeros() as usize;
        let mut digs = mdigs[bit];
        if self < C! { powers[digs as usize - 1] } {
            digs -= 1;
        }
        digs
    }
}

impl DigiCount for u16 {
    fn ͱ(self) -> u32 {
        self.checked_ilog10().ψ() + 1
    }
}

impl DigiCount for u8 {
    fn ͱ(self) -> u32 {
        self.checked_ilog10().ψ() + 1
    }
}

impl DigiCount for u128 {
    fn ͱ(self) -> u32 {
        self.checked_ilog10().ψ() + 1
    }
}

pub trait Ͷ: DigiCount {
    fn ͷ(self) -> impl Iterator<Item = u8>;
    fn Ͷ(self, i: u8) -> u8;
}

macro_rules! digs {
    ($for:ty) => {
        impl Ͷ for $for {
            fn ͷ(self) -> impl Iterator<Item = u8> {
                let digits = self.ͱ() as u8;
                (0..digits).rev().map(move |n| self.Ͷ(n))
            }
            fn Ͷ(self, i: u8) -> u8 {
                ((self / (10 as $for).pow(i as _)) % 10) as u8
            }
        }
    };
}
digs!(u128);
digs!(u64);
digs!(u32);
digs!(u16);
digs!(u8);

#[derive(Copy, Clone, PartialEq, PartialOrd)]
pub struct Ronge {
    pub begin: u16,
    pub end: u16,
}

impl Debug for Ronge {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}..{}", self.begin, self.end)
    }
}

impl Display for Ronge {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}..{}", self.begin, self.end)
    }
}

impl From<RangeInclusive<u16>> for Ronge {
    fn from(value: RangeInclusive<u16>) -> Self {
        Self {
            begin: *value.start(),
            end: *value.end(),
        }
    }
}

impl PartialEq<RangeInclusive<u16>> for Ronge {
    fn eq(&self, other: &RangeInclusive<u16>) -> bool {
        self == &Self::from(other.clone())
    }
}

impl Ronge {
    pub fn sane(self) -> bool {
        self.end >= self.begin
    }
    pub fn checked_len(self) -> Option<u16> {
        self.sane().then(|| self.len())
    }
    pub fn len(self) -> u16 {
        self.end - self.begin
    }

    /// push up
    pub fn pushu(&mut self, to: u16) {
        self.begin = self.begin.max(to);
    }

    /// push down
    pub fn pushd(&mut self, to: u16) {
        self.end = self.end.min(to);
    }

    pub fn intersect(self, with: Self) -> Self {
        Self {
            begin: self.begin.max(with.begin),
            end: self.end.min(with.end),
        }
    }

    pub fn news(&self, begin: u16) -> Self {
        Self {
            begin,
            end: self.end,
        }
    }

    pub fn newe(&self, end: u16) -> Self {
        Self {
            begin: self.begin,
            end,
        }
    }

    pub fn shrink(&mut self, with: Ronge) {
        self.pushu(with.begin);
        self.pushd(with.end);
    }
}

impl IntoIterator for Ronge {
    type Item = u16;

    type IntoIter = std::ops::Range<u16>;

    fn into_iter(self) -> Self::IntoIter {
        self.begin..self.end
    }
}

pub trait Μ where
    Self: Sized,
{
    fn μ(self, d: char) -> (Self, Self);
    fn μκ<T: FromStr>(self, d: char) -> impl Iterator<Item = (T, T)>
    where
        <T as FromStr>::Err: std::fmt::Display;

    fn μ1(self, d: char) -> Self {
        self.μ(d).1
    }

    fn μ0(self, d: char) -> Self {
        self.μ(d).0
    }

    fn between(self, a: char, b: char) -> Self {
        self.μ1(a).μ0(b)
    }
}

impl Μ for &[u8] {
    fn μ(self, d: char) -> (Self, Self) {
        let i = memchr::memchr(d as u8, self)
            .unwrap_or_else(|| shucks!("{} should split at {d} fine", self.p()));
        (&self[..i], &self[i + 1..])
    }

    fn μκ<T: FromStr>(self, d: char) -> impl Iterator<Item = (T, T)>
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        let (α, β) = self.μ(d);
        α.κ::<T>().zip(β.κ::<T>())
    }
}

pub fn gt<A: std::cmp::PartialOrd<T>, T>(n: T) -> impl Fn(A) -> bool {
    move |a| a > n
}

pub fn lt<A: std::cmp::PartialOrd<T>, T>(n: T) -> impl Fn(A) -> bool {
    move |a| a < n
}

impl Μ for &str {
    fn μ(self, d: char) -> (Self, Self) {
        self.split_once(d)
            .unwrap_or_else(|| shucks!("{self} should split at {d} fine"))
    }

    fn μκ<T: FromStr>(self, d: char) -> impl Iterator<Item = (T, T)>
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        let (α, β) = self.μ(d);
        α.κ::<T>().zip(β.κ::<T>())
    }
}

pub trait IterͶ: Iterator {
    fn ͷ(self) -> impl Iterator<Item = u8>;
}

impl<I: Iterator<Item = u64>> IterͶ for I {
    fn ͷ(self) -> impl Iterator<Item = u8> {
        self.flat_map(Ͷ::ͷ)
    }
}

pub trait TupleIterTools3<T, U, V>: Iterator {
    fn l(self) -> impl Iterator<Item = T>;
    fn m(self) -> impl Iterator<Item = U>;
    fn r(self) -> impl Iterator<Item = V>;
    fn lm(self) -> impl Iterator<Item = (T, U)>;
    fn lr(self) -> impl Iterator<Item = (T, V)>;
    fn mr(self) -> impl Iterator<Item = (U, V)>;
}

pub trait TupleIterTools2<T, U>: Iterator {
    fn l(self) -> impl Iterator<Item = T>;
    fn r(self) -> impl Iterator<Item = U>;
}

pub trait TupleIterTools2R<T, U>: Iterator {
    fn l(self) -> impl Iterator<Item = T>;
    fn r(self) -> impl Iterator<Item = U>;
}

pub fn l<R, T, U>(f: impl Fn(T) -> R) -> impl Fn((T, U)) -> R {
    move |(x, _)| f(x)
}
pub fn r<R, T, U>(f: impl Fn(U) -> R) -> impl Fn((T, U)) -> R {
    move |(_, x)| f(x)
}

pub trait FilterBy3<T, U, V>: Iterator {
    fn fl(self, f: impl Fn(T) -> bool) -> impl Iterator<Item = (T, U, V)>;
    fn fm(self, f: impl Fn(U) -> bool) -> impl Iterator<Item = (T, U, V)>;
    fn fr(self, f: impl Fn(V) -> bool) -> impl Iterator<Item = (T, U, V)>;
}

impl<T: Copy, U: Copy, V: Copy, I: Iterator<Item = (T, U, V)>> FilterBy3<T, U, V> for I {
    fn fl(self, f: impl Fn(T) -> bool) -> impl Iterator<Item = (T, U, V)> {
        self.filter(move |(x, _, _)| f(*x))
    }

    fn fm(self, f: impl Fn(U) -> bool) -> impl Iterator<Item = (T, U, V)> {
        self.filter(move |(_, x, _)| f(*x))
    }
    fn fr(self, f: impl Fn(V) -> bool) -> impl Iterator<Item = (T, U, V)> {
        self.filter(move |(_, _, x)| f(*x))
    }
}
pub trait FilterBy<T, U>: Iterator {
    fn fl(self, f: impl Fn(T) -> bool) -> impl Iterator<Item = (T, U)>;
    fn fr(self, f: impl Fn(U) -> bool) -> impl Iterator<Item = (T, U)>;
}

impl<T: Copy, U: Copy, I: Iterator<Item = (T, U)>> FilterBy<T, U> for I {
    fn fl(self, f: impl Fn(T) -> bool) -> impl Iterator<Item = (T, U)> {
        self.filter(move |(x, _)| f(*x))
    }

    fn fr(self, f: impl Fn(U) -> bool) -> impl Iterator<Item = (T, U)> {
        self.filter(move |(_, x)| f(*x))
    }
}

pub trait NumTupleIterTools {
    fn πολλαπλασιάζω_και_αθροίζω(&mut self) -> u64;
}

impl<I: Iterator<Item = (u64, u64)>> NumTupleIterTools for I {
    fn πολλαπλασιάζω_και_αθροίζω(&mut self) -> u64 {
        self.map(|(a, b)| a * b).sum()
    }
}

impl<T, U, I: Iterator<Item = (T, U)>> TupleIterTools2<T, U> for I {
    fn l(self) -> impl Iterator<Item = T> {
        self.map(|(x, _)| x)
    }

    fn r(self) -> impl Iterator<Item = U> {
        self.map(|(_, x)| x)
    }
}

impl<'a, T: Copy + 'a, U: Copy + 'a, I: Iterator<Item = &'a (T, U)>> TupleIterTools2R<T, U> for I {
    fn l(self) -> impl Iterator<Item = T> {
        self.map(|&(x, _)| x)
    }
    fn r(self) -> impl Iterator<Item = U> {
        self.map(|&(_, x)| x)
    }
}

impl<T, U, V, I: Iterator<Item = (T, U, V)>> TupleIterTools3<T, U, V> for I {
    fn l(self) -> impl Iterator<Item = T> {
        self.map(|(x, _, _)| x)
    }

    fn m(self) -> impl Iterator<Item = U> {
        self.map(|(_, x, _)| x)
    }

    fn r(self) -> impl Iterator<Item = V> {
        self.map(|(_, _, x)| x)
    }

    fn lm(self) -> impl Iterator<Item = (T, U)> {
        self.map(|(a, b, _)| (a, b))
    }

    fn lr(self) -> impl Iterator<Item = (T, V)> {
        self.map(|(a, _, b)| (a, b))
    }

    fn mr(self) -> impl Iterator<Item = (U, V)> {
        self.map(|(_, a, b)| (a, b))
    }
}

pub trait GreekTools<T>: Iterator {
    fn Δ(&mut self) -> T;
    fn ι<N>(&mut self) -> impl Iterator<Item = (T, N)>
    where
        Self: Ι<T, N>;
    fn ι1<N>(&mut self) -> impl Iterator<Item = (T, N)>
    where
        Self: Ι<T, N>;
    fn ν<const N: usize>(&mut self, into: &mut [T; N]) -> usize;
    fn Θ(&mut self);
}

pub trait ParseIter {
    fn κ<T: FromStr>(&mut self) -> impl Iterator<Item = T>
    where
        <T as FromStr>::Err: std::fmt::Display;
}

impl<'x, I: Iterator<Item = &'x [u8]>> ParseIter for I {
    fn κ<T: FromStr>(&mut self) -> impl Iterator<Item = T>
    where
        <T as FromStr>::Err: std::fmt::Display,
    {
        self.flat_map(|x| x.κ())
    }
}

pub trait Ι<T, N>: Iterator {
    fn ι(&mut self) -> impl Iterator<Item = (T, N)>;
    fn ι1(&mut self) -> impl Iterator<Item = (T, N)>;
}

macro_rules! ι {
    ($t:ty) => {
        impl<T, I: Iterator<Item = T>> Ι<T, $t> for I {
            fn ι(&mut self) -> impl Iterator<Item = (T, $t)> {
                self.zip(0..)
            }

            fn ι1(&mut self) -> impl Iterator<Item = (T, $t)> {
                self.zip(1..)
            }
        }
    };
}
ι!(i8);
ι!(u8);
ι!(u16);
ι!(u32);
ι!(u64);
ι!(usize);

pub fn nail<const N: usize, T: Copy>(x: &[T]) -> [T; N] {
    unsafe { (x.as_ptr() as *const [T; N]).read() }
}

pub mod reading {
    pub struct Integer<'a, 'b, T, const BY: u8 = b'\n'> {
        pub x: &'a mut &'b [u8],
        pub _ph: std::marker::PhantomData<T>,
    }

    impl<'a, 'b, T: Copy, const BY: u8> Integer<'a, 'b, T, BY> {
        pub fn new(x: &'a mut &'b [u8]) -> Self {
            Self {
                x,
                _ph: std::marker::PhantomData,
            }
        }
    }
    impl<
            'a,
            'b,
            const BY: u8,
            T: Default
                + std::ops::Mul<T, Output = T>
                + Add<T, Output = T>
                + From<u8>
                + Copy
                + Ten
                + Debug,
        > Iterator for Integer<'a, 'b, T, BY>
    {
        type Item = T;

        fn next(&mut self) -> Option<Self::Item> {
            (!self.x.is_empty()).then(|| read_until(self.x, BY))
        }
    }
    #[inline]
    pub fn 八(n: u64) -> u64 {
        // reinterpret as u64 ("92233721" => 92233721)
        // let n = u64::from_le_bytes(s);
        // combine 4 pairs of single digits:
        // split pieces into odd and even
        //  1_7_3_2_ (le repr)
        // _2_3_2_9
        // then combine
        // _21_37_23_92 (le repr, each byte as 2 digits)
        let n = ((n & 0x0f000f000f000f00) >> 8) + ((n & 0x000f000f000f000f) * 10);
        // combine 2 pairs of 2 digits:
        // split again
        // _21___23__
        // ___37___92
        // then combine
        // __14|137__36|7 (le repr, pipes separating bytes)
        let n = ((n & 0x00ff000000ff0000) >> 16) + ((n & 0x000000ff000000ff) * 100);
        // combine pair of 4 digits
        // split again
        // __14|137____ (then moved to ______14|137, as u64:3721)
        // ______36|07 (as u64: 9223)
        // then combine
        ((n & 0x0000ffff00000000) >> 32) + ((n & 0x000000000000ffff) * 10000)
    }

    use std::{
        io::{self, Read},
        ops::{Add, BitOrAssign, Shl},
    };
    pub trait Ext {
        fn rd<const N: usize>(&mut self) -> io::Result<[u8; N]>;
        fn by(&mut self) -> io::Result<u8> {
            Ok(self.rd::<1>()?[0])
        }
    }

    impl<T: Read> Ext for T {
        fn rd<const N: usize>(&mut self) -> io::Result<[u8; N]> {
            let mut buf = [0; N];
            self.read_exact(&mut buf)?;
            Ok(buf)
        }
    }
    use crate::util::prelude::*;
    pub fn κ<
        T: Default + std::ops::Mul<T, Output = T> + Add<T, Output = T> + From<u8> + Copy + Ten + Debug,
    >(
        x: &[u8],
        v: &mut [T],
    ) -> usize {
        let mut n = 0;
        let mut s = T::default();
        for &b in x {
            match b {
                b' ' => {
                    C! { v[n] = s };
                    n += 1;
                    s = T::default();
                }
                b => {
                    s = s * T::ten() + T::from(b - b'0');
                }
            }
        }
        C! {v[n] = s};
        n + 1
    }
    pub trait Ten {
        fn ten() -> Self;
    }
    macro_rules! tenz {
        ($for:ty) => {
            impl Ten for $for {
                fn ten() -> $for {
                    10
                }
            }
        };
    }
    tenz!(u8);
    tenz!(u16);
    tenz!(u32);
    tenz!(u64);
    tenz!(u128);
    tenz!(i8);
    tenz!(i16);
    tenz!(i32);
    tenz!(i64);
    tenz!(i128);

    const DIG: [u8; 256] = [
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    ];

    pub fn hex_dig(b: u8) -> u8 {
        DIG[b.nat()]
        // (b & 0xF) + 9 * (b >> 6)
    }

    pub fn hexN<
        T: From<u8> + TryFrom<usize> + Shl<T, Output = T> + BitOrAssign<T>,
        const N: usize,
    >(
        a: [u8; N],
    ) -> T {
        let mut c = T::from(hex_dig(a[0])) << T::try_from((N - 1) * 4).ψ();
        for (&n, sh) in a[1..].iter().zip((0..N - 1).rev()) {
            c |= T::from(hex_dig(n)) << T::try_from(sh * 4).ψ();
        }
        c
    }

    pub fn hex(mut d: &[u8]) -> Result<u32, ()> {
        let &b = d.take_first().ok_or(())?;
        let mut num = hex_dig(b) as u32;
        while let Some(&b) = d.take_first() {
            num = num * 16 + hex_dig(b) as u32;
        }
        Ok(num)
    }

    pub fn read_until<
        T: Default + std::ops::Mul<T, Output = T> + Add<T, Output = T> + From<u8> + Copy + Ten,
    >(
        x: &mut &[u8],
        until: u8,
    ) -> T {
        let mut n = T::from(x.by().ψ() - b'0');
        loop {
            let x = x.by().ψ();
            if x == until {
                return n;
            }
            n = n * T::ten() + T::from(x - b'0')
        }
    }

    pub fn 負迄(x: &mut &[u8], until: u8) -> i64 {
        let (sign, mut n) = match x.by().ψ() {
            b'-' => (-1, 0),
            b => (1, i64::from(b - b'0')),
        };
        loop {
            let byte = x.by().ψ();
            if byte == until {
                return n * sign as i64;
            }
            n = n * 10 + i64::from(byte - b'0');
        }
    }

    pub fn until<T: std::ops::Mul<T, Output = T> + Add<T, Output = T> + From<u8> + Copy + Ten>(
        x: &mut &[u8],
        until: u8,
    ) -> T {
        let mut n = T::from(x.by().ψ() - b'0');
        loop {
            let byte = x.by().ψ();
            if byte == until {
                return n;
            }
            n = n * T::ten() + T::from(byte - b'0');
        }
    }

    #[cfg_attr(debug_assertions, track_caller)]
    pub fn all<
        T: Default + std::ops::Mul<T, Output = T> + Add<T, Output = T> + From<u8> + Copy + Ten,
    >(
        x: &[u8],
    ) -> T {
        let mut n = T::default();
        for &byte in x {
            n = n * T::ten() + T::from(byte - b'0');
        }
        n
    }
}

pub fn even(x: &usize) -> bool {
    x % 2 == 0
}

impl<T, I: Iterator<Item = T>> GreekTools<T> for I {
    #[cfg_attr(debug_assertions, track_caller)]
    fn Δ(&mut self) -> T {
        self.next().ψ()
    }

    fn ν<const N: usize>(&mut self, into: &mut [T; N]) -> usize {
        let mut set = 0;
        for e in into {
            let Some(y) = self.next() else { break };
            *e = y;
            set += 1;
        }
        set
    }

    fn ι<N>(&mut self) -> impl Iterator<Item = (T, N)>
    where
        Self: Ι<T, N>,
    {
        self.ι()
    }

    fn ι1<N>(&mut self) -> impl Iterator<Item = (T, N)>
    where
        Self: Ι<T, N>,
    {
        self.ι1()
    }

    fn Θ(&mut self) {
        for _ in self {}
    }
}

pub trait TupleUtils<T, U> {
    fn mr<W>(self, f: impl FnOnce(U) -> W) -> (T, W);
    fn ml<V>(self, f: impl FnOnce(T) -> V) -> (V, U);
    fn rev(self) -> (U, T);
}

pub trait Widen<Wide> {
    fn nat(self) -> usize;
    fn widen(self) -> Wide;
}

macro_rules! wide {
    ($t:ty: $upper:ty) => {
        impl Widen<$upper> for $t {
            fn nat(self) -> usize {
                self as _
            }

            fn widen(self) -> $upper {
                self as _
            }
        }
    };
}
wide!(u8: u16);
wide!(u16: u32);
wide!(u32: u64);
wide!(u64: u128);

pub trait UnifiedTupleUtils<T> {
    fn mb<U>(self, f: impl FnMut(T) -> U) -> (U, U);
}

impl<T> UnifiedTupleUtils<T> for (T, T) {
    fn mb<U>(self, mut f: impl FnMut(T) -> U) -> (U, U) {
        (f(self.0), f(self.1))
    }
}

impl<T, U> TupleUtils<T, U> for (T, U) {
    fn mr<W>(self, f: impl FnOnce(U) -> W) -> (T, W) {
        (self.0, f(self.1))
    }
    fn ml<V>(self, f: impl FnOnce(T) -> V) -> (V, U) {
        (f(self.0), self.1)
    }
    fn rev(self) -> (U, T) {
        (self.1, self.0)
    }
}

#[allow(dead_code)]
fn cast_to<T: From<bool>>(x: bool, _to: T) -> T {
    x.into()
}

#[allow(unused_macros)]
macro_rules! bits {
    ($bitset:ident + $bit:expr) => {
        $bitset |= 1 << $bit
    };
    ($holder:ident[$index:expr] + $bit:expr) => {
        $holder[$index] |= 1 << $bit;
    };
    ($bitset:ident[$bit:expr]) => {
        ($bitset & 1 << $bit) != 0
    };
    ($holder:ident[$index:expr][$bit:expr]) => {
        ($holder[$index] & 1 << $bit) != 0
    };
    ($holder:ident[$index:expr][$index2:expr][$bit:expr]) => {
        ($holder[$index][$index2] & 1 << $bit) != 0
    };
    ($holder:ident[$index:expr][$index2:expr] + $bit:expr) => {
        $holder[$index][$index2] |= 1 << $bit
    };
    ($bitset:ident[$bit:expr] = $val:expr) => {
        $bitset = ($bitset & !(1 << $bit)) | (crate::util::cast_to($val, $bitset) << $bit)
    };
    ($bitset:ident - $bit:expr) => {
        $bitset &= !(1 << $bit)
    };
    ($bitset:ident ! $bit:expr) => {
        $bitset ^= 1 << $bit
    };
}
pub(crate) use bits;

pub struct Lines<'a> {
    bytes: &'a [u8],
}

impl<'a> Iterator for Lines<'a> {
    type Item = &'a [u8];

    fn next(&mut self) -> Option<Self::Item> {
        self.bytes.take_line()
    }
}

impl<'a> std::iter::FusedIterator for Lines<'a> {}

impl<'a> DoubleEndedIterator for Lines<'a> {
    #[inline]
    fn next_back(&mut self) -> Option<Self::Item> {
        self.bytes.take_backline()
    }
}

pub trait IntoLines {
    fn 行(&self) -> Lines<'_>;
}

impl<T: AsRef<[u8]>> IntoLines for T {
    fn 行(&self) -> Lines<'_> {
        Lines {
            bytes: self.as_ref(),
        }
    }
}

pub trait Printable {
    fn p(&self) -> impl std::fmt::Display;
}

struct PrintU8s<'a>(&'a [u8]);
impl std::fmt::Display for PrintU8s<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for &b in self.0 {
            if b.is_ascii() {
                f.write_char(b as char)?;
            } else {
                write!(f, "\\x{b:x}")?;
            }
        }
        Ok(())
    }
}

struct PrintManyU8s<'a, T: AsRef<[u8]>>(&'a [T]);
impl<T: AsRef<[u8]>> std::fmt::Display for PrintManyU8s<'_, T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        for row in self.0.as_ref() {
            write!(f, "{},", row.as_ref().p())?;
        }
        Ok(())
    }
}
impl Printable for [Vec<u8>] {
    fn p(&self) -> impl std::fmt::Display {
        PrintManyU8s(self)
    }
}

impl Printable for [&&[u8]] {
    fn p(&self) -> impl std::fmt::Display {
        PrintManyU8s(self)
    }
}

impl Printable for [&[u8]] {
    fn p(&self) -> impl std::fmt::Display {
        PrintManyU8s(self)
    }
}

impl Printable for [u8] {
    fn p(&self) -> impl std::fmt::Display {
        PrintU8s(self)
    }
}

impl Printable for Vec<u8> {
    fn p(&self) -> impl std::fmt::Display {
        PrintU8s(self)
    }
}

pub fn sort<T: Ord>(mut x: Vec<T>) -> Vec<T> {
    x.sort_unstable();
    x
}

pub trait TakeLine<'b> {
    fn take_line<'a>(&'a mut self) -> Option<&'b [u8]>;
    fn take_backline<'a>(&'a mut self) -> Option<&'b [u8]>;
}

impl<'b> TakeLine<'b> for &'b [u8] {
    fn take_line<'a>(&'a mut self) -> Option<&'b [u8]> {
        match memchr::memchr(b'\n', self) {
            None if self.is_empty() => None,
            None => Some(std::mem::replace(self, b"")),
            Some(end) => {
                let line = C! { &self[..end]};
                *self = C! { &self[end + 1..]};
                Some(line)
            }
        }
    }

    fn take_backline<'a>(&'a mut self) -> Option<&'b [u8]> {
        let end = self.len().checked_sub(1)?;
        match memchr::memrchr(b'\n', &self[..end]) {
            None => Some(std::mem::replace(self, b"")),
            Some(end) => {
                let line = &self[end + 1..];
                *self = &self[..end];
                Some(line)
            }
        }
    }
}

impl<'b> TakeLine<'b> for &'b str {
    fn take_line<'a>(&'a mut self) -> Option<&'b [u8]> {
        match memchr::memchr(b'\n', self.as_bytes()) {
            None if self.is_empty() => None,
            None => Some(std::mem::replace(self, "").as_bytes()),
            Some(end) => {
                let line = self[..end].as_bytes();
                *self = &self[end + 1..];
                Some(line)
            }
        }
    }

    fn take_backline<'a>(&'a mut self) -> Option<&'b [u8]> {
        let end = self.len().checked_sub(1)?;
        match memchr::memrchr(b'\n', &self.as_bytes()[..end]) {
            None => Some(std::mem::replace(self, "").as_bytes()),
            Some(end) => {
                let line = &self[end + 1..];
                *self = &self[..end];
                Some(line.as_bytes())
            }
        }
    }
}

pub trait IntoCombinations<T: Copy>: Iterator {
    /// LEAKY
    fn combine(self) -> impl Iterator<Item = (T, T)>;
}

impl<T: Copy + 'static, I: Iterator<Item = T>> IntoCombinations<T> for I {
    fn combine(self) -> impl Iterator<Item = (T, T)> {
        let x = Box::leak(self.collect::<Box<[_]>>());
        x.iter()
            .enumerate()
            .flat_map(|(i, &a)| x[i..].iter().map(move |&b| (a, b)))
    }
}

pub trait Skip {
    fn skip(&mut self, n: usize);
    fn skip_n(&mut self, n: &'static str) {
        self.skip(n.len())
    }
}

impl<T> Skip for &[T] {
    #[cfg_attr(debug_assertions, track_caller)]
    fn skip(&mut self, n: usize) {
        if cfg!(debug_assertions) {
            *self = &self[n..];
        } else {
            *self = C! { &self[n..] };
        }
    }
}

impl Skip for &str {
    #[cfg_attr(debug_assertions, track_caller)]
    fn skip(&mut self, n: usize) {
        if cfg!(debug_assertions) {
            *self = &self[n..];
        } else {
            *self = C! { &self[n..] };
        }
    }
}

/// WYRAND based rng's
pub mod rand {
    /// WYRAND
    pub fn u64() -> u64 {
        static mut STATE: u64 = 0;
        let tmp = unsafe {
            STATE = STATE.wrapping_add(0x60bee2bee120fc15);
            (STATE as u128).wrapping_mul(0xa3b195354a39b70d)
        };
        let m1 = (tmp >> 64) ^ tmp;
        let tmp = m1.wrapping_mul(0x1b03738712fad5c9);
        ((tmp >> 64) ^ tmp) as u64
    }

    pub fn u32() -> u32 {
        u64() as u32
    }

    pub fn u16() -> u16 {
        u64() as u16
    }

    pub fn f32() -> f32 {
        (1.0 / ((1u32 << 24) as f32)) * ((u32() >> 8) as f32)
    }

    pub fn f64() -> f64 {
        (1.0 / ((1u64 << 53) as f64)) * ((u64() >> 11) as f64)
    }
}