#include<bits/stdc++.h>
using namespace std;
#define int short
#define eps 1e-8
int n,h[2005][2],l[2005][2];
long long ans;
vector<long double>H[2005],L[2005];
struct node{int x,y;}a[10];
void solve(){
	cin>>n;
	for(int i=1;i<=n;i++)cin>>a[i].x>>a[i].y;
	a[0]=a[n];
	for(int i=1;i<=n;i++)
		if(a[i].x==a[i-1].x){
			for(int j=a[i-1].y;j<=a[i].y;j++)if(!H[j].size()||abs(H[j][H[j].size()-1]-a[i].x)>eps)H[j].push_back(a[i].x);
			for(int j=a[i-1].y;j>=a[i].y;j--)if(!H[j].size()||abs(H[j][H[j].size()-1]-a[i].x)>eps)H[j].push_back(a[i].x);
		}else if(a[i].y==a[i-1].y){
			for(int j=a[i-1].x;j<=a[i].x;j++)if(!L[j].size()||abs(L[j][L[j].size()-1]-a[i].y)>eps)L[j].push_back(a[i].y);
			for(int j=a[i-1].x;j>=a[i].x;j--)if(!L[j].size()||abs(L[j][L[j].size()-1]-a[i].y)>eps)L[j].push_back(a[i].y);
		}else {
			long double k=(long double)(a[i-1].y-a[i].y)/(a[i-1].x-a[i].x),b=a[i].y-k*a[i].x;
			for(int j=a[i-1].x;j<=a[i].x;j++)if(!L[j].size()||abs(L[j][L[j].size()-1]-(k*j+b))>eps)L[j].push_back(k*j+b);
			for(int j=a[i-1].x;j>=a[i].x;j--)if(!L[j].size()||abs(L[j][L[j].size()-1]-(k*j+b))>eps)L[j].push_back(k*j+b);
			for(int j=a[i-1].y;j<=a[i].y;j++)if(!H[j].size()||abs(H[j][H[j].size()-1]-(j-b)/k)>eps)H[j].push_back((j-b)/k);
			for(int j=a[i-1].y;j>=a[i].y;j--)if(!H[j].size()||abs(H[j][H[j].size()-1]-(j-b)/k)>eps)H[j].push_back((j-b)/k);
		}
	for(int i=0;i<=2000;i++){
		if(H[i].size()==1)H[i].push_back(H[i][0]);
		if(L[i].size()==1)L[i].push_back(L[i][0]);
		if(H[i].size()>=2){
			if(H[i][0]>H[i][1])swap(H[i][0],H[i][1]);
			h[i][0]=ceil(H[i][0]-eps),h[i][1]=floor(H[i][1]+eps);
		}else h[i][1]=-1;
		if(L[i].size()>=2){
			if(L[i][0]>L[i][1])swap(L[i][0],L[i][1]);
			l[i][0]=ceil(L[i][0]-eps),l[i][1]=floor(L[i][1]+eps);
		}else l[i][1]=-1;
	}
	for(int i=0;i<=2000;i++)
		for(int j=h[i][0];j<=h[i][1];j++)
			for(int k=0;i+k<=2000;k++){
				if(j<h[i+k][0]||j+k>h[i][1]||j+k>h[i+k][1])break;
				if(k==0)ans+=min(min(l[j][1]-i,j-h[i][0]),min(i-l[j][0],h[i][1]-j));
				else ans+=1+min(min(l[j][1]-i,j-h[i][0]),min(i-l[j][0],h[i][1]-j))+min((i-l[j][0],h[i][1]-j-k),min(l[j+k][1]-i-k,j-h[i+k][0]));
			}
	cout<<ans<<'\n';
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0),solve();
	return 0;
}