#include<bits/stdc++.h>
using namespace std;
#define ll long long
int x,x2,y,y2;
long long ans=0;
bool a[40][40]={0};

void dfs(int xz,int yz){
	if(a[xz+1][yz]==0&&xz+1<21) dfs(xz+1,yz);
	if(a[xz][yz+1]==0&&yz+1<21) dfs(xz,yz+1);
	if(a[xz][yz]==a[x][y]){
		ans++;
		return;
	}
}

int main()
{
	cin>>x>>y>>x2>>y2;
	a[x2+2][y2+1]=1;
	a[x2+2][y2-1]=1;
	a[x2-2][y2+1]=1;
	a[x2-2][y2-1]=1;
	a[x2+1][y2+2]=1;
	a[x2-1][y2+2]=1;
	a[x2+1][y2-2]=1;
	a[x2-1][y2-2]=1;
	a[x2][y2]=1;
	dfs(0,0);
	cout<<ans;
	return 0;
}