#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int m,n,m1,m2;
unsigned long long a[25][25],f[25][25];
int main(){
	scanf("%d%d%d%d",&m,&n,&m1,&m2);
	a[m1][m2]=1;
	a[m1-1][m2-2]=1;a[m1-2][m2-1]=1;a[m1-2][m2+1]=1;a[m1-1][m2+2]=1;
	a[m1+1][m2-2]=1;a[m1+2][m2-1]=1;a[m1+2][m2+1]=1;a[m1+1][m2+2]=1;
	for(int i=0;i<=m;i++){
		for(int j=0;j<=n;j++){
			if(i==0&&a[i][j]==0)f[i][j]=1;
			if(j==0&&a[i][j]==0)f[i][j]=1;
		}
	}
	for(int i=1;i<=m;i++){
		for(int j=1;j<=n;j++){
			if(a[i][j]==0)f[i][j]=f[i-1][j]+f[i][j-1];
		}
	}
	printf("%lld",f[m][n]);
	return 0;
}