#include <iostream>
using namespace std;
int dx[] = {0, -2, -1, 1, 2, 2, 1, -1, -2}, dy[] = {0, -1, -2, -2, -1, 1, 2, 2, 1};
int x1, x2, m1, m2;
const int N = 25;
long f[N][N], st[N][N];
int main()
{
    cin >> x1 >> x2 >> m1 >> m2;
    for (int i = 0; i <= x1; ++ i ) f[i][0] = 1;
    for (int i = 0; i <= x2; ++ i ) f[0][i] = 1;
    for (int i = 0; i < 9; ++ i )
    {
        int o = m1 + dx[i], p = m2 + dy[i];
        if (o >= 1 && o <= x1 && p >= 1 && p <= x2)
        st[o][p] = 1;
    }
    for (int i = 1; i <= x1; ++ i )
        for (int j = 1; j <= x2; ++ j )
        {
            if (st[i][j] == 1) continue;
            f[i][j] = f[i][j - 1] + f[i - 1][j];
        }
    cout << f[x1][x2];
    return 0;
}