#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using ll = long long;
using mint = atcoder::modint998244353;

int H, W, A, B;
int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> H >> W >> A >> B;
    mint s1h = 0, s2h = 0, s1w = 0, s2w = 0;
    for(int i = 1;i <= H;i++){
        mint v = min({A, i, H - i + 1});
        s1h += v;
        s2h += v * v;
    }
    for(int i = 1;i <= W;i++){
        mint v = min({B, i, W - i + 1});
        s1w += v;
        s2w += v * v;
    }
    mint q = (ll)(H - A + 1) * (W - B + 1);
    mint w = s2h * s2w - 2 * q * s1h * s1w + q * q * H * W;
    mint ans = (ll)H * W - w / q / q;
    cout << ans.val() << endl;
    return 0;
}