#include<bits/stdc++.h>
using namespace std;
const int dir[8][2] = { {1,2},{1,-2},{2,1},{2,-1},{-1,2},{-1,-2},{-2,1},{-2,-1} };
bool d[30][30];
long long dp[30][30], n, m, cx, cy;
int main() {
    cin >> n >> m >> cx >> cy;
    d[cx][cy] = true;
    for (int i = 0; i < 8; i++) {
        int tx = cx + dir[i][0], ty = cy + dir[i][1];
        if (tx >= 0 && tx <= n && ty >= 0 && ty <= m) d[tx][ty] = true;
    }
    dp[0][0] = 1;
    for (int i = 0; i <= n; i++) {
        for (int j = 0; j <= m; j++) {
            if (d[i][j] == false) {
                if (i) dp[i][j] += dp[i - 1][j];
                if (j) dp[i][j] += dp[i][j - 1];
            }
        }
    }
    cout << dp[n][m] << endl;
    return 0;
}