#include<bits/stdc++.h>
using namespace std;
bool s[30][30];
int a,b,c,d,ans=0;
void dfs(int x,int y,int k)
{
	if(s[x][y])
	{
		return;
	}
	if(x==a&&y==b)
	{
		ans++;
		return;
	}
	s[x][y]=1;
	dfs(x+1,y,k+1);
	dfs(x,y+1,k+1);
	s[x][y]=0;
}
int main()
{
	
	cin >> a >> b >> c >> d;
	s[c-1][d-2]=1;
	s[c-2][d-1]=1;
	s[c-1][d+2]=1;
	s[c-2][d+1]=1;
	s[c+1][d-2]=1;
	s[c+2][d-1]=1;
	s[c+1][d+2]=1;
	s[c+2][d+1]=1;
	dfs(0,0,0);
	cout << ans;
	return 0;
}