#include "iostream"
#define int long long
using namespace std;
int s[25][25],t[25][25];
signed main(){
	int n,m,x,y;
	cin>>n>>m>>x>>y;
	t[1][1]=1;
	x++;
	y++;
	n++;
	m++;
	s[x][y]=1;
	s[x-1][y+2]=1;
	s[x-1][y-2]=1;
	s[x-2][y+1]=1;
	s[x-2][y-1]=1;
	s[x+1][y+2]=1;
	s[x+1][y-2]=1;
	s[x+2][y+1]=1;
	s[x+2][y-1]=1;
	for(int i=0;i<=n;i++){
		for(int j=0;j<=m;j++){
			if((i!=1||j!=1)&&!s[i][j])t[i][j]=t[i-1][j]+t[i][j-1];
		}
	}
	cout<<t[n][m];
	return 0;
}