#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);
const long long MOD = 998244353;

long long f[500000], g[500000];

long long comb(long long n, long long r) {
  return (f[n] * g[r] % MOD ) * g[n-r] % MOD;
}

long long modpow(long long x, long long p, long long mod) {
  long long ret = 1;
  while (p) {
    if (p & 1)
      ret = ret * x % mod;
    x = x * x % mod;
    p >>= 1;
  }
  return ret;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  long long n, m, a, b;
  cin >> n >> m >> a >> b;
  
  f[0] = 1, g[0] = 1;
  for (int i = 1; i < 500000; i++) f[i] = i * f[i-1] % MOD;
  for (int i = 1; i < 500000; i++) g[i] = modpow(f[i], MOD - 2, MOD);

  long long ret = 0;
  for (long long h = 1; h <= m; h++) {
    long long t = h + (n - 1) * a;
    if (t > h + b) continue;
    if (t > m) continue;
    long long d = min(m - t, h + b - t);
    (ret += comb(n+d-1, d)) %= MOD;
  }

  cout << (ret * f[n]) % MOD << endl;
  
  return 0;
}