#include <bits/stdc++.h>
using namespace std;
int n, m, x, y, f[1005][1005], ban[1005][1005];
int main()
{
    cin >> n >> m >> x >> y;
    ban[x][y] = 1;
    if(x - 2 >= 0 && y - 1 >= 0)ban[x - 2][y - 1] = 1;
    if(x - 2 >= 0)ban[x - 2][y + 1] = 1;
    if(x - 1 >= 0 && y - 2 >= 0)ban[x - 1][y - 2] = 1;
    if(x - 1 >= 0)ban[x - 1][y + 2] = 1;
    if(y - 1 >= 0)ban[x + 2][y - 1] = 1;
    ban[x + 2][y + 1] = 1;
    if(y - 2 >= 0)ban[x + 1][y - 2] = 1;
    ban[x + 1][y + 2] = 1;
    if(!ban[0][0])f[0][0] = 1;
    for(int i = 1; i <= n; i++)if(!ban[i][0])f[i][0] = f[i - 1][0];
    for(int i = 1; i <= m; i++)if(!ban[0][i])f[0][i] = f[0][i - 1];
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= m; j++)
            if(!ban[i][j])f[i][j] = f[i][j - 1] + f[i - 1][j];
    cout << f[n][m] << "\n";
    return 0;
}