#include<iostream> 
using namespace std;
int f[21][21],n,m,a,b,sum=0;
void dg(int x,int y)
{
	if(x==n && y==m){
		sum++;
	}
	if(f[x][y]==1){
		return ;
	}
	if(x+1<=n){
		dg(x+1,y);
	}
	if(y+1<=m){
		dg(x,y+1);
	}
}
int main()
{
	cin>>n>>m>>a>>b;
	f[a][b]=f[a-2][b-1]=f[a-1][b-2]=f[a+1][b-2]=f[a+2][b-1]=f[a+2][b+1]=f[a+1][b+2]=f[a-1][b+2]=f[a-2][b+1]=1;
	dg(0,0);
	cout<<sum;
	return 0;
}