#include <bits/stdc++.h>
template <class T>
void chkmin(T &x, const T &y) {
  if (x > y) x = y;
}
template <class T>
void chkmax(T &x, const T &y) {
  if (x < y) x = y;
}
using ll = long long;
const int N = 2010;

struct point {
  int x, y;
  point operator-(const point &rhs) const { return {x - rhs.x, y - rhs.y}; }
  bool operator==(const point &rhs) const { return x == rhs.x && y == rhs.y; }
};
ll cross(const point &a, const point &b) {
  return (ll)a.x * b.y - (ll)a.y * b.x;
}

int main() {
  std::cin.tie(0)->sync_with_stdio(0);
  int n;
  std::cin >> n;
  std::vector<point> a(n);
  for (auto &[x, y] : a) std::cin >> x >> y;
  std::array<int, N> rowl, rowr, coll, colr;
  rowl.fill(1e9), rowr.fill(-1e9), coll.fill(1e9), colr.fill(-1e9);
  auto check = [&](point u) {
    for (int i = 0; i < n; i++) {
      auto l = a[i ? i - 1 : n - 1], m = a[i], r = a[(i + 1) % n];
      auto v1 = l - m, v2 = r - m;
      if (cross(v1, v2) == 0) continue;
      if (cross(v1, v2) < 0) std::swap(v1, v2);
      if (cross(v1, u - m) < 0) return false;
      if (cross(u - m, v2) < 0) return false;
    }
    return true;
  };
  for (int i = 0; i < N; i++)
    for (int j = 0; j < N; j++)
      if (check({i, j})) {
        chkmin(rowl[i], j), chkmax(rowr[i], j);
        chkmin(coll[j], i), chkmax(colr[j], i);
      }
  int ans = 0;
  for (int i = 0; i < N; i++) {
    if (rowl[i] > rowr[i]) continue;
    for (int j = i + 1; j < N; j++) {
      if (rowl[j] > rowr[j]) continue;
      int d = j - i;
      for (int k = 0; k + d < N; k++) {
        if (coll[k] > colr[k]) continue;
        if (coll[k + d] > colr[k + d]) continue;
        int l1 = rowl[i] - k, r1 = rowr[i] - k;
        int l2 = k + d - rowr[j], r2 = k + d - rowl[j];
        int l3 = j - colr[k], r3 = j - coll[k];
        int l4 = coll[k + d] - i, r4 = colr[k + d] - i;
        ans += std::max(
            0, std::min({r1, r2, r3, r4, d}) - std::max({l1, l2, l3, l4, 1}) + 1);
      }
    }
  }
  std::cout << ans << '\n';
}