#include<bits/stdc++.h>
using namespace std;
long long x,y,bx,by,ans=0;
int a[50][50];
void dfs(int xi,int yi)
{
	if(xi==bx&&yi==by)
	{
		ans++;
		return ;
	}
	if(a[xi][yi]==1)
		return ;
	if(xi<0||yi<0||xi>bx||yi>by)
		return ;
	a[xi][yi]=1;
	dfs(xi+1,yi);
	dfs(xi,yi-1);
	a[xi][yi]=0;
}
int main(){
	cin>>bx>>by>>x>>y;
	a[x][y] = 1;
	a[x-1][y-2] = 1;
	a[x-1][y+2] = 1;
	a[x-2][y-1] = 1;
	a[x-2][y+1] = 1;
	a[x+1][y-2] = 1;
	a[x+1][y+2] = 1;
	a[x+2][y-1] = 1;
	a[x+2][y+1] = 1;
	dfs(0,0);
	cout<<ans;
	return 0;
}