#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
const int MAX = 600005;
vector<long long> fac(MAX, 1), finv(MAX, 1), inv(MAX, 1);
void COMinit() {
    for (int i = 2; i < MAX; i++) {
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}
long long COM(long long n, long long k) {
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
int main() {
  cin.tie(0); cout.tie(0);
  ios::sync_with_stdio(false);
  COMinit();
  int X, Y, Z, W;
  cin >> X >> Y >> Z >> W;
  if(Z == 0) {
    cout << COM(X + Y - Z - W - 1, X - 1) * COM(X, Z) % MOD * fac[X - Z] % MOD * COM(Y, W) % MOD * fac[Y - W] % MOD << '\n';
  } else {
    cout << COM(X + Y - Z - W - 1, Y - 1) * COM(X, Z) % MOD * fac[X - Z] % MOD * COM(Y, W) % MOD * fac[Y - W] % MOD << '\n';
  }
  return 0;
}