#include<iostream>
using namespace std;
long long qipan[21][21];
int main()
{
    long long n , m , a , b;
    cin >> n >> m >> a >> b;
    for(long long i = 0 ; i <= n ; i++)
    {
        qipan[i][0] = 1;
    }
    for(long long i = 0 ; i <= m ; i++)
    {
        qipan[0][i] = 1;
    }
    for(long long i = 1 ; i <= n ; i++)
    {
        for(long long j = 1 ; j <= m ; j++)
        {
            if((i == a + 1 && j == b - 2)||(i == a - 1 && j == b + 2)||(i == a + 2 && j == b - 1)||(i == a - 2 && j == b + 1)||(i == a + 2 && j == b + 1)||(i == a + 1 && j == b + 2)||(i == a - 1 && j == b - 2)||(i == a - 2 && j == b - 1)||(i == a && j == b)) qipan[i][j] = 0;
            else qipan[i][j] = qipan[i][j - 1] + qipan[i - 1][j];
        }
    }
    cout << qipan[n][m];
    return 0;
}