#include<bits/stdc++.h>
using namespace std;
const int m=2000;
int n,l[m+5],r[m+5],x[15],y[15];
vector<double>tmp[m+5];
signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	cin>>n;
	for(int i=1;i<=n;++i)cin>>x[i]>>y[i];
	x[0]=x[n],y[0]=y[n];
	int mnx=m+1,mny=m+1,mxx=0,mxy=0;
	for(int i=0;i<n;++i){
		int x1=x[i],x2=x[i+1],y1=y[i],y2=y[i+1];
		mnx=min(mnx,x1);
		mxx=max(mxx,x1);
		mny=min(mny,y1);
		mxy=max(mxy,y1);
		if(y1>y2)swap(y1,y2),swap(x1,x2);
		if(y1==y2){
			tmp[y1].push_back(x1);
			tmp[y1].push_back(x2);
		}
		else{
			for(int j=y1;j<=y2;++j){
				tmp[j].push_back((double)(x1*(y2-j)+x2*(j-y1))/(y2-y1));
			}
		}
	}
	int s=max(mxx-mnx,mxy-mny);
	for(int i=0;i<=m;++i){
		if(tmp[i].empty()){
			l[i]=0;
			r[i]=-1;
			continue;
		}
		sort(tmp[i].begin(),tmp[i].end());
		l[i]=(int)ceil(tmp[i][0]);
		r[i]=(int)floor(tmp[i].back());
	}
	long long ans=0;
	for(int i=0;i<=s;++i)
	for(int j=1;i+j<=s;++j){
//		int xx[4]={0,i,i+j,j},yy[4]={0,j,j-i,-i};
		for(int k=0;k+i+j<=m;++k){
			int 
			tl=max(max(l[k],l[k+i]-j),max(l[k+i+j]-j+i,l[k+j]+i)),
			tr=min(min(r[k],r[k+i]-j),min(r[k+i+j]-j+i,r[k+j]+i));
			ans+=max(0,tr-tl+1);
		}
	}
	cout<<ans;
}