#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 998244353;
vector<long long> fact, fact_inv, inv;
void init_nCk(int SIZE) {
    fact.resize(SIZE + 5);
    fact_inv.resize(SIZE + 5);
    inv.resize(SIZE + 5);
    fact[0] = fact[1] = 1;
    fact_inv[0] = fact_inv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < SIZE + 5; i++) {
        fact[i] = fact[i - 1] * i % mod;
        inv[i] = mod - inv[mod % i] * (mod / i) % mod;
        fact_inv[i] = fact_inv[i - 1] * inv[i] % mod;
    }
}
long long nCk(int n, int k) {
    if(n < k || n < 0 || k < 0) return 0;
    return fact[n] * (fact_inv[k] * fact_inv[n - k] % mod) % mod;
}
signed main(){
	init_nCk(700000);
	int a,b,c,d;
	cin>>a>>b>>c,d;
	if(c == 0){
		swap(c,d);
		swap(a,b);
	}
	int ans = nCk(a+b-c-1,b-1);
	for(int i=1;i<=b;i++) ans = (ans*i)%mod;
	for(int i=a;i>c;i--) ans = (ans*i)%mod;
	cout<<(ans+mod)%mod<<endl;
}