#include <bits/stdc++.h>
using namespace std;
const int N = 2e3 + 10, V = 2000;

int n, x[15], y[15], l[N], r[N];
double zl[N], zr[N];

int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; ++i) scanf("%d%d", x + i, y + i);
    for (int i = 0; i <= V; ++i) zl[i] = V, zr[i] = 0;
    for (int i = 0; i < n; ++i) {
        int sx = x[i], sy = y[i], tx = x[(i + 1) % n], ty = y[(i + 1) % n];
        if (sx == tx) { zl[sx] = min(zl[sx], 1. * min(sy, ty)), zr[sx] = max(zr[sx], 1. * max(sy, ty)); continue; }
        if (sx > tx) swap(sx, tx), swap(sy, ty);
        double k = 1. * (ty - sy) / (tx - sx);
        for (int j = sx; j <= tx; ++j) {
            double v = sy + k * (j - sx);
            zl[j] = min(zl[j], v), zr[j] = max(zr[j], v);
        }
    }
    int L = V, R = 0;
    for (int i = 0; i <= V; ++i) {
        l[i] = ceil(zl[i]), r[i] = floor(zr[i]);
        if (l[i] <= r[i]) L = min(L, i), R = max(R, i);
    }
    int lim = max(*max_element(x, x + n) - *min_element(x, x + n), *max_element(y, y + n) - *min_element(y, y + n));
    long long ans = 0;
    for (int a = 0; a <= lim; ++a)
        for (int b = 1; a + b <= lim; ++b)
            for (int i = L; i + a + b <= R; ++i) {
                int ql = max({l[i], l[i + a] - b, l[i + b] + a, l[i + a + b] - b + a});
                int qr = min({r[i], r[i + a] - b, r[i + b] + a, r[i + a + b] - b + a});
                if (ql <= qr) ans += qr - ql + 1;
            }
    printf("%lld\n", ans);
    return 0;
}