#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define pii pair<int,int>
#define piii tuple<int,int,int>
#define mp make_pair
#define mt make_tuple
#define fi first
#define x first
#define y second
#define se second
#define ins insert
#define let(a...) int a;tie(a)
#define deb(var) cerr<<#var<<'='<<(var)<<"; "
#define int long long

const int W=2000;
int n;
pii g[10];
void acrec(){
	int w=g[3].x-g[2].x,h=g[2].y-g[1].y,ans=0;
	for(int x=-W;x<=W;x++){
		for(int y=-W;y<=W;y++){
			if(x==0||y==0)continue;
			int b=abs(x)+abs(y);
			ans+=max(w-b+1,0ll)*max(h-b+1,0ll);
		}
	}							cout<<ans/4<<'\n';
}
void actri(){
	
}
void work(){
	cin>>n;
	for(int i=1;i<=n;i++)
		cin>>g[i].x>>g[i].y;
	if(n==4)return acrec();
	if(n==3)return actri();
}
signed main(){
	ios::sync_with_stdio(0),
	cin.tie(0),cout.tie(0);
	int T=1;while(T--)work();
}