#include <bits/stdc++.h>
using namespace std;
int main(){
    long long a,b,c,d;
    cin>>a>>b>>c>>d;
    long long e[a+10][b+10]{};
    for(long long i=1;i<=b;i++){
		e[0][i]=1;
		if((0==c+1&&i==d-2)||(0==c+1&&i==d+2)||(0==c-1&&i==d-2)||(0==c-1&&i==d+2)||(0==c+2&&i==d-1)||(0==c+2&&i==d+1)||(0==c-2&&i==d+1)||(0==c-2&&i==d-1)||(0==c&&i==d)){
		    e[0][i]=0;
		}
	}
    for(long long i=1;i<=a;i++){
		e[i][0]=1;
		if((i==c+1&&0==d-2)||(i==c+1&&0==d+2)||(i==c-1&&0==d-2)||(i==c-1&&0==d+2)||(i==c+2&&0==d-1)||(i==c+2&&0==d+1)||(i==c-2&&0==d+1)||(i==c-2&&0==d-1)||(i==c&&0==d)){
	        e[i][0]=0;
		}
	}
    for(long long i=1;i<=a;i++){
        for(long long j=1;j<=b;j++){
            e[i][j]=e[i-1][j]+e[i][j-1];
            if((i==c+1&&j==d-2)||(i==c+1&&j==d+2)||(i==c-1&&j==d-2)||(i==c-1&&j==d+2)||(i==c+2&&j==d-1)||(i==c+2&&j==d+1)||(i==c-2&&j==d+1)||(i==c-2&&j==d-1)||(i==c&&j==d)){
                e[i][j]=0;
            }
        }
    }
    cout<<e[a][b];
    return 0;
}