#include <bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i, first, last) for (int i = (first); i <= (last); ++i)
#define DOW(i, first, last) for (int i = (first); i >= (last); --i)
const int m = 2000;
int n, lx[m + 5], rx[m + 5], ly[m + 5], ry[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;
  REP(i, 1, n) cin >> x[i] >> y[i];
  int mnx = m + 1, mny = m + 1, mxx = 0, mxy = 0;
  REP(i, 1, n) {
    int x1 = x[i], x2 = x[i % n + 1], y1 = y[i], y2 = y[i % n + 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);
  REP(i, 0, m) {
    if (!tmp[i].size()) {
      lx[i] = 0;
      rx[i] = -1;
      continue;
    }
    sort(tmp[i].begin(), tmp[i].end());
    lx[i] = (int)ceil(tmp[i][0]);
    rx[i] = (int)floor(tmp[i].back());
  }
  int ans = 0;
  REP(i, 0, s) REP(j, 1, s - i) REP(k, 0, m - i - j) {
    int l = max({lx[k], lx[k + i] - j, lx[k + i + j] - (j - i), lx[k + j] + i});
    int r = min({rx[k], rx[k + i] - j, rx[k + i + j] - (j - i), rx[k + j] + i});
    // cout << l << ' ' << r << '\n';
    if (r >= l) ans += r - l + 1;
  }
  cout << ans << '\n';
}