Problem:
Score : 700 points

Problem Statement

Takahashi has a tower which is divided into N layers.
Initially, all the layers are uncolored. Takahashi is going to paint some of the layers in red, green or blue to make a beautiful tower.
He defines the beauty of the tower as follows:

The beauty of the tower is the sum of the scores of the N layers, where the score of a layer is A if the layer is painted red, A+B if the layer is painted green, B if the layer is painted blue, and 0 if the layer is uncolored.

Here, A and B are positive integer constants given beforehand. Also note that a layer may not be painted in two or more colors.

Takahashi is planning to paint the tower so that the beauty of the tower becomes exactly K.
How many such ways are there to paint the tower? Find the count modulo 998244353.
Two ways to paint the tower are considered different when there exists a layer that is painted in different colors, or a layer that is painted in some color in one of the ways and not in the other.

Constraints

1 ≤ N ≤ 3×10^5

1 ≤ A,B ≤ 3×10^5

0 ≤ K ≤ 18×10^{10}

All values in the input are integers.

Input

Input is given from Standard Input in the following format:

N A B K

Output

Print the number of the ways to paint tiles, modulo 998244353.

Sample Input 1

4 1 2 5

Sample Output 1

40

In this case, a red layer worth 1 points, a green layer worth 3 points and the blue layer worth 2 points. The beauty of the tower is 5 when we have one of the following sets of painted layers:

1 green, 1 blue

1 red, 2 blues

2 reds, 1 green

3 reds, 1 blue

The total number of the ways to produce them is 40.

Sample Input 2

2 5 6 0

Sample Output 2

1

The beauty of the tower is 0 only when all the layers are uncolored. Thus, the answer is 1.

Sample Input 3

90081 33447 90629 6391049189

Sample Output 3

577742975

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

fn main() {
    let (n, mut a, mut b, k): (usize, usize, usize, usize) = readln();
    let mut answer: Mint = 0.into();
    let mut fact: Vec<Mint> = vec![1.into()];
    let mut inv_fact: Vec<Mint> = vec![1.into()];
    for i in 1..300010 {
        let next = fact[fact.len()-1] * i;
        fact.push(next);
    }
    for i in 1..300010 {
        let next = inv_fact[inv_fact.len()-1] / i;
        inv_fact.push(next);
    }
    if a < b {
        std::mem::swap(&mut b, &mut a);
    }
    let mut a = 0;
    for x in 0..n+1 {
        let rest = k as isize - (a * x) as isize;
        if rest < 0 {
            break;
        }
        if (rest as usize) % b == 0 {
            let y = (rest as usize) / b;
            let ri = n as isize - (x + y) as isize;
            let lb = if ri >= 0 { 0 } else { (-ri) as usize };
            let ub = min(x, y);
            for z in lb..ub+1 {
                let r = (ri + z as isize) as usize;
                a += 1;
                //answer += inv_fact[x-z] * inv_fact[y-z] * inv_fact[z] * inv_fact[r];
            }
        }
    }
    println!("{}", a);
    //println!("{}", answer * fact[n]);
}

#[allow(unused_imports)]
use std::cmp::{max, min};
#[allow(unused_imports)]
use std::collections::{HashMap, HashSet, VecDeque};

pub trait FromLn {
    fn fromln(s: &str) -> Self;
}
pub fn readln<T: FromLn>() -> T {
    let mut buf = String::new();
    let _ = ::std::io::stdin().read_line(&mut buf).unwrap();
    T::fromln(buf.trim())
}
pub fn readlns<T: FromLn>(n: usize) -> Vec<T> {
    let mut vs = vec![];
    for _ in 0..n {
        vs.push(readln());
    }
    vs
}
macro_rules! fromln_primitives {
    ($($t:ty),*) => { $(
        impl FromLn for $t {
            fn fromln(s: &str) -> $t {
                s.parse().unwrap()
            }
        }
    )* }
}
fromln_primitives!(
    String,
    bool,
    f32,
    f64,
    isize,
    i8,
    i16,
    i32,
    i64,
    usize,
    u8,
    u16,
    u32,
    u64
);
impl<T> FromLn for Vec<T>
where
    T: FromLn,
{
    fn fromln(s: &str) -> Vec<T> {
        s.split_whitespace().map(T::fromln).collect()
    }
}
impl FromLn for Vec<char> {
    fn fromln(s: &str) -> Vec<char> {
        s.chars().collect()
    }
}
macro_rules! fromln_tuple {
    ($($t:ident),*) => {
        impl<$($t),*> FromLn for ($($t),*) where $($t: FromLn),* {
            fn fromln(s: &str) -> ($($t),*) {
                let mut it = s.split_whitespace();
                let t = ($($t::fromln(it.next().unwrap())),*);
                assert_eq!(it.next(), None);
                t
            }
        }
    }
}
fromln_tuple!(A, B);
fromln_tuple!(A, B, C);
fromln_tuple!(A, B, C, D);
fromln_tuple!(A, B, C, D, E);
fromln_tuple!(A, B, C, D, E, F);

pub const MOD: u32 = 998244353;

//TODO: It has to be generics on MOD value.
//TODO: https://github.com/rust-lang/rust/issues/44580 may be releated
#[derive(Debug, Copy, Clone, Eq)]
pub struct Mint {
    val: u32,
}

impl<T: Into<Mint>> std::ops::Add<T> for Mint {
    type Output = Mint;

    fn add(self, other: T) -> Mint {
        let nval = self.val + other.into().val;
        Mint {
            val: if nval >= MOD { nval - MOD } else { nval },
        }
    }
}

impl<T: Into<Mint>> std::ops::Sub<T> for Mint {
    type Output = Mint;

    fn sub(self, other: T) -> Mint {
        let nval = self.val + MOD - other.into().val;
        Mint {
            val: if nval >= MOD { nval - MOD } else { nval },
        }
    }
}

impl<T: Into<Mint>> std::ops::Mul<T> for Mint {
    type Output = Mint;

    fn mul(self, other: T) -> Mint {
        let nval = self.val as u64 * other.into().val as u64;
        Mint {
            val: (nval % (MOD as u64)) as u32,
        }
    }
}

impl<T: Into<Mint>> std::ops::Div<T> for Mint {
    type Output = Mint;

    fn div(self, other: T) -> Mint {
        self * other.into().inv()
    }
}

impl Mint {
    pub fn inv(self) -> Mint {
        let mut a = self.val as i32;
        let mut b = MOD as i32;
        let mut u = 1 as i32;
        let mut v = 0 as i32;
        while b != 0 {
            let t = a / b;
            a -= t * b;
            std::mem::swap(&mut a, &mut b);
            u -= t * v;
            std::mem::swap(&mut u, &mut v);
        }
        Mint {
            val: if u < 0 { u + MOD as i32 } else { u } as u32,
        }
    }
}

impl PartialEq for Mint {
    fn eq(&self, other: &Mint) -> bool {
        self.val == other.val
    }
}

impl std::fmt::Display for Mint {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        self.val.fmt(f)
    }
}

macro_rules! impl_signed_mint {
    ($($t:ty)*) => ($(
        impl From<$t> for Mint {
            #[inline]
            fn from(x: $t) -> Mint {
                let t = (x as i64) % (MOD as i64);
                if x >= 0 {
                    Mint{ val: t as u32 }
                } else {
                    Mint{ val: (MOD as i64 + t) as u32 }
                }
            }
        }
    )*)
}

macro_rules! impl_unsigned_mint {
    ($($t:ty)*) => ($(
        impl From<$t> for Mint {
            #[inline]
            fn from(x: $t) -> Mint {
                let t = x as u64 % MOD as u64;
                Mint{ val: t as u32 }
            }
        }
    )*)
}

impl_signed_mint! { i8 i16 i32 i64 isize }
impl_unsigned_mint! { u8 u16 u32 u64 usize }

impl<T: Into<Mint>> std::ops::AddAssign<T> for Mint {
    fn add_assign(&mut self, other: T) {
        *self = *self + other.into();
    }
}

impl<T: Into<Mint>> std::ops::SubAssign<T> for Mint {
    fn sub_assign(&mut self, other: T) {
        *self = *self - other.into();
    }
}

impl<T: Into<Mint>> std::ops::MulAssign<T> for Mint {
    fn mul_assign(&mut self, other: T) {
        *self = *self * other.into();
    }
}

impl<T: Into<Mint>> std::ops::DivAssign<T> for Mint {
    fn div_assign(&mut self, other: T) {
        *self = *self / other.into();
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_simple() {
        let a: Mint = Mint::from(3);
        let b: Mint = Mint::from(1000000000);
        assert_eq!(Mint::from(3000000000u64 % MOD as u64), a * b);
    }
}