#include <bits/stdc++.h>
using namespace std;
int n;
int odd, even;
int miny[400001], maxy[400001], min2y[400001], max2y[400001];
vector<int> p[400001];
int main() {
  ios::sync_with_stdio(false);
  cin >> n;
  for (int i = 0; i <= 2e5; i++) {
    maxy[i] = -1, miny[i] = 2e5 + 1;
  }
  for (int i = 1; i <= n; i++) {
    int u, v, x, y;
    cin >> u >> v;
    x = v - u;
    y = u + v;
    x += 2e5;
    y += 2e5;
    p[x].push_back(y);
  }
  for (int i = 0; i <= 4e5; i++) {
    sort(p[i].begin(), p[i].end());
    miny[i] = min2y[i] = 4e5 + 1;
    maxy[i] = max2y[i] = -1;
  }
  for (int i = 1; i <= 4e5; i++) {
    if (i > 1) maxy[i] = maxy[i - 2];
    if (i > 1) miny[i] = miny[i - 2];
    if (!p[i - 1].empty()) maxy[i] = max(maxy[i], p[i - 1].back() - 1);
    if (!p[i - 1].empty()) miny[i] = min(miny[i], p[i - 1][0] + 1);
  }
  long long ans = 0;
  for (int i = 4e5 - 1; i >= 0; i--) {
    if (i < 4e5 - 1) max2y[i] = max2y[i + 2];
    if (i < 4e5 - 1) min2y[i] = min2y[i + 2];
    if (!p[i + 1].empty()) max2y[i] = max(max2y[i], p[i + 1].back() - 1);
    if (!p[i + 1].empty()) min2y[i] = min(min2y[i], p[i + 1][0] + 1);
    maxy[i] = min(maxy[i], max2y[i]);
    miny[i] = max(miny[i], min2y[i]);
    if (maxy[i] >= miny[i]) {
      ans += (maxy[i] - miny[i]) / 2 + 1;
    }
  }
  cout << ans << endl;
}
