#include<iostream>
using namespace std;
int main(){
	int m,n,b[25][25]={0},x,y;
	long long a[25][25]={0};
	cin>>n>>m>>x>>y;
	n+=2;
	m+=2;
	x+=2;
	y+=2;
	a[2][2]=1;
	b[x-1][y-2]=1;
	b[x-1][y+2]=1;
	b[x+1][y-2]=1;
	b[x+1][y+2]=1;
	b[x+2][y-1]=1;
	b[x+2][y+1]=1;
	b[x-2][y+1]=1;
	b[x-2][y-1]=1;
	b[x][y]=1;
	for(int i=2;i<=n;i++){
		for(int j=2;j<=m;j++){
			if(b[i][j]==0)
				if(i>2&&j>2)
					a[i][j]=a[i-1][j]+a[i][j-1];
				else a[i][j]=1;
		}
	}
	cout<<a[n][m];
	return 0;
}