#include <bits/stdc++.h>
using namespace std;

int main(){
	int x,y,n,m;
	int b[21][21]={0};
	cin>>n>>m>>x>>y;
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			b[i][j]=1;
		}
	}
	b[x][y]=0;
	b[x+2][y+1]=0;
	b[x+1][y+2]=0;
	b[x-1][y+2]=0;
	b[x-2][y+1]=0;
	b[x-2][y-1]=0;
	b[x-1][y-2]=0;
	b[x+1][y-2]=0;
	b[x+2][y-1]=0;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(b[i][j]!=0){
				b[i][j]=b[i-1][j]+b[i][j-1];
			}
		}
	}
	cout<<b[n][m];
}