//#pragma GCC optimize(3,"Ofast","inline")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e3 + 10, M = 2e3;
int n, l[N], r[N], x[N], y[N];
int sx, sy, dx, dy, dis;
ll ans;
vector<double> vec[N];
inline ll read(){
	ll x = 0, m = 1;
	char ch = getchar();
	while(!isdigit(ch)){
		if(ch == '-') m = -1;
		ch = getchar();
	}
	while(isdigit(ch)){
		x = (x << 1) + (x << 3) + (ch ^ 48);
		ch = getchar();
	}
	return x * m;
}
inline void write(ll x){
	if(x < 0){
		putchar('-');
		write(-x);
		return;
	}
	if(x >= 10) write(x / 10);
	putchar(x % 10 + '0');
}
signed main(){
//	freopen("PKUSCD1T2.in", "r", stdin);
	//freopen(".out", "w", stdout);
	n = read();
	for(int i = 1; i <= n; ++ i) x[i] = read(), y[i] = read();
	x[0] = x[n], y[0] = y[n], sx = sy = M + 1, dx = dy = 0;
	for(int i = 0; i < n; ++ i){
		int x1 = x[i], x2 = x[i + 1], y1 = y[i], y2 = y[i + 1];
		sx = min(sx, x1), sy = min(sy, y1);
		dx = max(dx, x1), dy = max(dy, y1);
		if(y1 > y2) swap(x1, x2), swap(y1, y2);
		if(y1 == y2) vec[y1].push_back(x1), vec[y1].push_back(x2);
		else for(int j = y1; j <= y2; ++ j) vec[j].push_back(((double)(x1 * (y2 - j) + x2 * (j - y1))) / (y2 - y1));
	}dis = max(dx - sx, dy - sy);
	for(int i = 0; i < N; ++ i){
		if(!vec[i].size()){l[i] = 0, r[i] = -1; continue;}
		sort(vec[i].begin(), vec[i].end());
		l[i] = (int) ceil(vec[i][0]), r[i] = floor(vec[i].back());
	}
	for(int i = 0; i <= dis; ++ i){
		for(int j = 1; i + j <= dis; ++ j){
			for(int k = 0; i + j + k <= M; ++ k){
				int L = max(max(l[k], l[i + k] - j), max(l[i + j + k] - j + i, l[j + k] + i));
				int R = min(min(r[k], r[i + k] - j), min(r[i + j + k] - j + i, r[j + k] + i));
				ans += max(R - L + 1ll, 0ll);
			}
		}
	}
	write(ans);
	return 0;
}