#include <bits/stdc++.h>
#include <atcoder/modint>

using namespace std;
using namespace atcoder;
using ll = long long;

using mint = modint998244353;

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

    //2*L c1*i c2*i - L^2 c1*i*i c2*i*i

    ll H, W, A, B, hx, hy, wx, wy;
    cin >> H >> W >> A >> B;
    if (A*2 <= H) hx = A-1, hy = H-A*2+2;
    else hx = H-A, hy = H-(H-A)*2;
    if (B*2 <= W) wx = B-1, wy = W-B*2+2;
    else wx = W-B, wy = W-(W-B)*2;

    mint L = mint((H-A+1) * (W-B+1)).inv(), ans=0;
    ans += L * 2 * (hx+hy) * (hx+1) * (wx+wy) * (wx+1);
    ans -= L * L * (hx*(hx+1)*(2*hx+1)/3 + hy*(hx+1)*(hx+1)) * (wx*(wx+1)*(2*wx+1)/3 + wy*(wx+1)*(wx+1));
    
    cout << ans.val() << endl;

    return 0;
}