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

using mint = modint998244353;

int main(){
    int h,w,a,b;
    cin >> h >> w >> a >> b;
    mint ans = 0;
    for(int x0 = 0;x0 <= h-a;x0++){
        for(int y0 = 0;y0 <= w-b;y0++){
            for(int x1 = 0;x1 <= h-a;x1++){
                for(int y1 = 0;y1 <= w-b;y1++){
                    vector<vector<int>> board(h,vector<int>(w));
                    for(int i = x0;i < x0+a;i++){
                        for(int j = y0;j < y0+b;j++){
                            board[i][j] = 1;
                        }
                    }
                    for(int i = x1;i < x1+a;i++){
                        for(int j = y1;j < y1+b;j++){
                            board[i][j] = 1;
                        }
                    }
                    int count = 0;
                    for(int i = 0;i < h;i++){
                        for(int j = 0;j < w;j++){
                            count += board[i][j];
                        }
                    }
                    mint ad = count;
                    ad /= mint(h-a+1)*mint(w-b+1);
                    ad /= mint(h-a+1)*mint(w-b+1);
                    ans += ad;
                }
            }
        }
    }
    cout << ans.val() << endl;
}