#include<iostream>
#include<cmath>
using namespace std;
int main(){
	int  r[23][23]={0},n,m,x,y;
    cin>>n>>m>>x>>y;
    for(int i=1;i<=n;i++){
    	for(int j=1;j<=m;j++){
			r[i][j]=r[i-1][j]+r[i][j-1]; 
			r[1][1]=1;
			r[1][2]=1;
			r[2][1]=1;
			r[x][y]=0;
			r[x-1][y-2]=0;
			r[x-1][y+2]=0;
			r[x+1][y-2]=0;
			r[x+1][y+2]=0;
			r[x+2][y-1]=0;
			r[x+2][y+1]=0;
			r[x-2][y-1]=0;
			r[x-2][y+1]=0;
		}
	}
	cout<<r[n][m];
    return 0; 
}