#include <iostream>
#include <cstdio>
using namespace std;
int n,m,x,y,ax[25][25],lj;
void dfs(int a,int b)
{
	if(a==n&&b==m)
	{
		lj++;
		return;
	}
	else
	{
		if(a<=n&&b<=m&&a>=1&&b>=1&&ax[a][b]==0)
		{
			ax[a][b]=1;
			dfs(a+1,b);
			dfs(a,b+1);
			ax[a][b]=0;
		}
	}
}
int main()
{
	freopen("pj024.in","r",stdin);
	freopen("pj024.out","w",stdout);
	cin>>n>>m>>x>>y;
	n++;
	m++;
	x++;
	y++;
	ax[x][y]=-1;
	ax[x+1][y+2]=-1;
	ax[x+2][y+1]=-1;
	ax[x+2][y-1]=-1;
	ax[x+1][y-2]=-1;
	ax[x-1][y-2]=-1;
	ax[x-2][y-1]=-1;
	ax[x-2][y+1]=-1;
	ax[x-1][y+2]=-1;
	dfs(1,1);
	cout<<lj<<endl;
	return 0;
}