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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.*;
import java.util.*;
 
 
public class Main implements Runnable {
 
  public static final int MOD = 998244353;

  public void run() {
    Scanner scanner = new Scanner(System.in);

    long n = scanner.nextLong();
    long a = scanner.nextLong(); 
    long b = scanner.nextLong(); 
    long k = scanner.nextLong();

    long[][] fact = calcFact((int)n + 1);
    long res = 0;
    for (int i = 0 ; i <= k / a && i <= n ; i ++) {
      if ((k - a * i) % b == 0) {
        long j = (k - a * i) / b;
        if (j <= n) {
          res += comb(fact, (int)n, (int)i) * comb(fact, (int)n, (int)j) % MOD;
          res %= MOD;
        }
      }
    }

    System.out.println(res);
  }

  public long div(long a, long b) {
    return a * pow(b, MOD - 2) % MOD;
  }

  public long pow(long a, long b) {
    if (b == 0) {
      return 1;
    } else if (b % 2 == 0) {
      long d = pow(a, b / 2);
      return (d * d) % MOD;
    } else {
      long d = pow(a, b - 1);
      return (a * d) % MOD;
    }
  }

  public long[][] calcFact(int n) {
    long[] fact = new long[n];
    long[] invfact = new long[n];
    fact[0] = 1;
    for (int i = 1 ; i < n ; i ++) {
      fact[i] = (fact[i - 1] * i) % MOD;
    }
    invfact[n - 1] = pow(fact[n - 1], MOD - 2);
    for (int i = n - 2 ; i >= 0 ; i --) {
      invfact[i] = invfact[i + 1] * (i + 1) % MOD;
    }
    return new long[][]{fact, invfact};
  }

  public long comb(long[][] fact, int n, int r) {
    long res = fact[0][n];
    res *= fact[1][n - r];
    res %= MOD;
    res *= fact[1][r];
    res %= MOD;
    return res;
  }

  public static void main(String[] args) {
    Main main = new Main();
    main.run();
  }
 
  // scanner slightly faster than usual ones
  public static class BetterScanner {
 
    private InputStream stream;
    private byte[] buffer = new byte[1024];
    private int pointer = 0;
    private int bufferLength = 0;
 
    public BetterScanner(InputStream stream) {
      this.stream = stream;
    }
 
    private boolean updateBuffer() {
      if (pointer >= bufferLength) {
        pointer = 0;
        try {
          bufferLength = stream.read(buffer);
        } catch (IOException exception) {
          exception.printStackTrace();
        }
        return bufferLength > 0;
      } else {
        return true;
      }
    }
 
    private int read() {
      if (updateBuffer()) {
        return buffer[pointer ++];
      } else {
        return -1;
      }
    }
 
    public boolean hasNext() {
      skipUnprintable();
      return updateBuffer();
    }
 
    private void skipUnprintable() { 
      while (updateBuffer() && !isPrintableChar(buffer[pointer])) {
        pointer ++;
      }
    }
 
    public String next() {
      if (hasNext()) {
        StringBuilder builder = new StringBuilder();
        int codePoint = read();
        while (isPrintableChar(codePoint)) {
          builder.appendCodePoint(codePoint);
          codePoint = read();
        }
        return builder.toString();
      } else {
        throw new NoSuchElementException();
      }
    }
 
    public long nextLong() {
      if (hasNext()) {
        long number = 0;
        boolean minus = false;
        int codePoint = read();
        if (codePoint == '-') {
          minus = true;
          codePoint = read();
        }
        if (codePoint >= '0' && codePoint <= '9') {
          while (true) {
            if (codePoint >= '0' && codePoint <= '9') {
              number *= 10;
              number += codePoint - '0';
            } else if (codePoint < 0 || !isPrintableChar(codePoint)) {
              return (minus) ? -number : number;
            } else {
              throw new NumberFormatException();
            }
            codePoint = read();
          }
        } else {
          throw new NumberFormatException();
        }
      } else {
        throw new NoSuchElementException();
      }
    }
 
    public int nextInt() {
      long number = nextLong();
      if (number >= Integer.MIN_VALUE && number <= Integer.MAX_VALUE) {
        return (int)number;
      } else {
        throw new NumberFormatException();
      }
    }
 
    private boolean isPrintableChar(int codePoint) {
      return codePoint >= 33 && codePoint <= 126;
    }
 
  }
 
}