#include <iostream>
using namespace std;

#define N 25

int n, m, x, y;
bool kill[N][N];
long long f[N][N];

void init() {
    f[1][1] = 1;
    kill[x][y] = true;
    kill[x - 2][y - 1] = true;
    kill[x - 2][y + 1] = true;
    kill[x + 2][y - 1] = true;
    kill[x + 2][y + 1] = true;
    kill[x - 1][y + 2] = true;
    kill[x - 1][y - 2] = true;
    kill[x + 1][y + 2] = true;
    kill[x + 1][y - 2] = true;
}

int main() {
    cin >> n >> m >> x >> y;
    n++, m++, x++, y++;

    init();

    for (int i = 1; i <= n; i++) for (int j = 1; j <= m; j++) {
        if ((i != 1 || j != 1) && !kill[i][j])
            f[i][j] = f[i - 1][j] + f[i][j - 1];
    }

    cout << f[n][m] << endl;
    return 0;
}