#include <stdio.h>
int main()
{
    long long a,b,c,d;
    scanf("%lld%lld%lld%lld",&a,&b,&c,&d);
    long long qipan[a+1][b+1];
    for (int i = 0; i < a+1; i++)
    {
        for (int j = 0; j < b+1; j++)
        {
            qipan[i][j]=1;
        }
    }
    qipan[c][d]=0;
    qipan[c-2][d-1]=0;
    qipan[c-2][d+1]=0;
    qipan[c+2][d-1]=0;
    qipan[c+2][d+1]=0;
    qipan[c-1][d-2]=0;
    qipan[c-1][d+2]=0;
    qipan[c+1][d-2]=0;
    qipan[c+1][d+2]=0;
    /*for (int i = 0; i < a+1; i++)
    {
        for (int j = 0; j < b+1; j++)
        {
            printf("%lld ",qipan[i][j]);
        }
        printf("\n");
    }*/
    qipan[0][0]=1;
    for(int i=0; i<a+1; i++)
    {
        for(int j=0; j<b+1; j++)
        {
            if(qipan[i][j]==0)
            {
                continue;
            }
            if(i==0&&j==0)
            {
                qipan[i][j]=1;
                continue;
            }
            if(i==0)
            {
                qipan[i][j]=qipan[i][j-1];
                continue;
            }
            if(j==0)
            {
                qipan[i][j]=qipan[i-1][j];
                continue;
            }
            qipan[i][j]=qipan[i-1][j]+qipan[i][j-1];
        }
    }
    printf("%lld",qipan[a][b]);
    return 0;
}