#include <iostream>
#include <cstring> 
#include <map>
#include <vector>
#include <queue>
#include <cmath>
#include <algorithm>
#include <set>
// #include <bits/stdc++.h>
// 
#define int long long
#define For(i,a,b) for(int i=(a);i<=(b);i++)
#define Rof(i,a,b) for(int i=(a);i>=(b);i--)
#define Grf(it,u,to) for(int it=he[u],to;(to=e[it],it);it=nxt[it]) 
#define In __inline 
#define OP operator
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
namespace Mine {
	// mt19937_64 wql(514);
	In int read() {
		ll x=1,a=0;
		char ch=getchar();
		while(ch>'9' || ch<'0') x=(ch=='-')?-1:x,ch=getchar();
		while(ch>='0' && ch<='9') a=(a<<1)+(a<<3)+(ch-'0'),ch=getchar();
		return a*x;
	} const int N=10,M=2005;
	int n;
	struct point {
		int x,y;
		point(int a=0,int b=0){x=a,y=b;}
	} a[N];
	point OP + (point x,point y) {
		return point(x.x+y.x,x.y+y.y);
	}
	point OP - (point x,point y) {
		return point(x.x-y.x,x.y-y.y);
	}
	int OP * (point x,point y) {
		return x.x*y.y-y.x*x.y;
	}
	int area(point a0,point a1,point x) {
		return (a1-a0)*(x-a0);
	}
	namespace S0 {
		void solve0() {
			int A=a[2].y-a[1].y,B=a[3].x-a[2].x;
			int b=min(A,B),ret=0;
			For(i,1,b) {
				ret+=i*(A-i+1)*(B-i+1);
			} printf("%lld\n",ret);
		}
	}
	int mx,my;
	namespace S1 {
		int lowy[M],upy[M];
		bool ans[M];
		bool check(point x) {
			int ret=area(a[n],a[1],x)<=0;
			// printf("%lld ",area(a[n],a[1],x));
			For(i,1,n-1) {
				ret&=(area(a[i],a[i+1],x)<=0);
				if(!ret) break;
			}
			return ret;
		}
		void solve1(){
			int res=0;
			memset(lowy,0x3f,sizeof lowy);
			
			For(x,0,mx) {
				For(y,0,my) {
					ans[y]=check(point(x,y));
					// printf("%d ",ans[y]);
				}
				// puts("");
				int low=my+10,up=0;
				For(i,0,my) {
					if(ans[i]) low=min(low,i),up=max(up,i);
				}
				lowy[x]=low,upy[x]=up;
			} For(a,1,mx) {
				For(b,0,my) {
					// if(!a && !b) continue;
					For(x,0,mx) {
						int x0=x,x1=x+a,x2=x+b,x3=x+a+b;
						if(x3>mx) continue;
						int low=max(max(lowy[x0]-b,lowy[x1]),max(lowy[x2]-a-b,lowy[x3]-a));
						int up=min(min(upy[x0]-b,upy[x1]),min(upy[x2]-a-b,upy[x3]-a));
						if(up>=low)res+=up-low+1;
						// printf("%lld %lld %lld %lld\n",a,b,x,low);
					}
				}
			} 
			printf("%lld",res);
			
		}
	}
	
	namespace S2 {
		int lowy[M],upy[M];
		bool ans[M];
		bool check(point x) {
			int ret=area(a[n],a[1],x)<=0;
			// printf("%lld ",area(a[n],a[1],x));
			For(i,1,n-1) {
				ret&=(area(a[i],a[i+1],x)<=0);
				if(!ret) break;
			}
			return ret;
		}
		void solve2(){
			int res=0;
			memset(lowy,0x3f,sizeof lowy);
			
			For(x,0,mx) {
				For(y,0,my) {
					ans[y]=check(point(x,y));
					// printf("%d ",ans[y]);
				}
				// puts("");
				int low=my+10,up=0;
				For(i,0,my) {
					if(ans[i]) low=min(low,i),up=max(up,i);
				}
				lowy[x]=low,upy[x]=up;
			} For(a,1,mx) {
				For(b,0,my) {
					// if(!a && !b) continue;
					For(x,0,mx) {
						int x0=x,x1=x+a,x2=x+b,x3=x+a+b;
						if(x3>mx) continue;
						int low=max(max(lowy[x0]-b,lowy[x1]),max(lowy[x2]-a-b,lowy[x3]-a));
						int up=min(min(upy[x0]-b,upy[x1]),min(upy[x2]-a-b,upy[x3]-a));
						if(up>=low)res+=up-low+1;
						else break;
						// printf("%lld %lld %lld %lld\n",a,b,x,low);
					}
				}
			} 
			printf("%lld",res);
			
		}
	}
	signed main() {
		n=read();
		For(i,1,n) {
			int x=read(),y=read();
			a[i]=point(x,y);
			mx=max(mx,x);my=max(my,y);
		}
		if(n==4 && a[1].x==a[2].x && a[2].y==a[3].y && a[3].x==a[4].x && a[4].y==a[1].y)
			S0::solve0();
		else if(n==3 && a[1].x==a[2].x && a[1].y==a[3].y)
			S2::solve2();
		else S1::solve1();
		return 0;
	}
}signed main() {
	// freopen("name.in","r",stdin);
	// freopen("name.out","w",stdout);
	return Mine::main();
}