#include <bits/stdc++.h>
using namespace std;

#include "atcoder/modint.hpp"
using mint = atcoder::modint998244353;

int main() {
    int h, w, a, b;
    cin >> h >> w >> a >> b;
    assert(1 <= a and a <= h and h <= 200000);
    assert(1 <= b and b <= w and w <= 200000);

    auto f = [&](int n, int k) -> mint {
        // return \sum_{i=0}^{n} i (k + i)
        return mint(n) * (n + 1) / 2 * mint(k) + mint(n) * (n + 1) * (2 * n + 1) / 6;
    };

    int l    = max(1, 2 * a - h);
    int r    = a - 1;
    mint row = mint(2) * (f(r, h - 2 * a + 1) - f(l - 1, h - 2 * a + 1));
    row += mint(a) * (h - a + 1);

    l        = max(1, 2 * b - w);
    r        = b - 1;
    mint col = mint(2) * (f(r, w - 2 * b + 1) - f(l - 1, w - 2 * b + 1));
    col += mint(b) * (w - b + 1);

    mint ans = row * col;
    ans /= mint(h - a + 1).pow(2) * mint(w - b + 1).pow(2);
    ans = mint(2) * a * b - ans;
    cout << ans.val() << endl;
}