#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001


int main(){
	
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	
	long long H,W,A,B;
	cin>>H>>W>>A>>B;
	
	mint t = A;
	t *= B;
	t *= H-A+1;
	t *= W-B+1;
	t *= H-A+1;
	t *= W-B+1;
	t *= 2;
	mint h = 0,w = 0;
	rep(_,2){
		for(int i=A-1;true;i--){
			int x = 0,y = A-1,z = i,w = i+A-1;
			int d = max(y,w) - min(x,z) + 1;
			if(d >= A*2)break;
			mint tt = A*2 - d;
			tt *= max(0LL,H - d + 1);
			h += tt;
		}
		swap(h,w);
		swap(H,W);
		swap(A,B);
	}
	//cout<<h.val()<<' '<<w.val()<<endl;
	t -= h * w;
	t /= H-A+1;
	t /= W-B+1;
	t /= H-A+1;
	t /= W-B+1;
	cout<<t.val()<<endl;
	
	return 0;
}