#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pr pair<int, int>
#define pb push_back
#define mid (l + r) / 2
#define ls num << 1
#define rs num << 1 | 1

inline int read() {
    int x = 0, m = 1;
    char ch = getchar();

    while (!isdigit(ch)) {
        if (ch == '-') m = -1;
        ch = getchar();
    }

    while (isdigit(ch)) {
        x = x * 10 + 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');
}

#define double long double

const double eps = 1e-8;

struct node {
    int x, y;
} a[10];

int l[2005][2];
vector<double> L[2005];

signed main() {
    int n = read();
    for (int i = 1; i <= n; i++) a[i].x = read(), a[i].y = read();
    a[0] = a[n];
    for (int i = 1; i <= n; i++) {
        if (a[i].x == a[i - 1].x) continue;
        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 {
            double k = (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 i = 0; i <= 2000; i++) {
        if (L[i].size() == 1) L[i].push_back(L[i][0]);
        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;
    }
    ll ans = 0;
    for (int i = 0; i <= 2000; i++) {
        for (int j = 1; i + j <= 2000; j++) {
            for (int k = 0; i + j + k <= 2000; k++) {
                ans += max(0, min({l[k][1], l[i + k][1] - j, l[i + j + k][1] + i - j}) - max({l[k][0], l[j + k][0] + i, l[i + j + k][0] + i - j}) + 1);
            }
        }
    }
    write(ans);
    return 0;
}