#include<stdio.h>
int main(){
    int m,n;
    int p,q;
    scanf("%d%d%d%d",&m,&n,&p,&q);
    long long A[25][25]={0};
    int i=0,j=0;
    for(i=0;i<m+1;i++){
        for(j=0;j<n+1;j++){
            if((i==p&&j==q)||
            (i==p+1&&j==q+2)||
            (i==p+2&&j==q+1)||
            (i==p+1&&j==q-2)||
            (i==p+2&&j==q-1)||
            (i==p-1&&j==q-2)||
            (i==p-2&&j==q-1)||
            (i==p-1&&j==q+2)||
            (i==p-2&&j==q+1)){
                A[i][j]=(long long)0;
            }else{
                if(i==0||j==0){
                    A[i][j]=(long long)1;
                }else{
                    A[i][j]=A[i-1][j]+A[i][j-1];
                }
            }
        }
    }
    printf("%lld",A[m][n]);
    return 0;
}