#include <bits/stdc++.h>
using namespace std;
vector<pair<int, int> > mas[2];
int a[(int)1e5 + 10], b[(int)1e5 + 10];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int x, y;
    cin >> x >> y;
    int a = abs((x + y) % 2);
    mas[a].push_back({(x + y - a) / 2, (x - y - a) / 2});
  }
  long long ans = 0;
  for (int i = 0; i < 2; i++) {
    sort(mas[i].begin(), mas[i].end());
    a[mas[i].size()] = (int)-3e5;
    b[mas[i].size()] = (int)3e6;
    for (int j = (int)mas[i].size() - 1; j >= 0; j--) {
      a[j] = max(a[j + 1], mas[i][j].second);
      b[j] = min(b[j + 1], mas[i][j].second);
    }
    int c = (int)-3e5;
    int d = (int)3e5;
    for (int j = 0; j + 2 < (int)mas[i].size(); j++) {
      c = max(c, mas[i][j].second);
      d = min(d, mas[i][j].second);
      long long le = max(b[j + 1], d);
      long long ri = min(a[j + 1], c);
      if (ri > le) {
        ans += (ri - le) * (mas[i][j + 1].first - mas[i][j].first);
      }
    }
  }
  cout << ans << endl;
  return 0;
}
