#include <bits/stdc++.h>   using namespace std;   const int MAX = 1e5 + 6.66;   const int MAXN = MAX << 2;   const int N = MAX << 1;   pair<int, int> p[MAX];   int up[MAXN];   int down[MAXN];   int uppre[MAXN], upsuf[MAXN], downpre[MAXN], downsuf[MAXN];   int main() {     memset(down, 63, sizeof down);     memset(downpre, 63, sizeof downpre);     memset(downsuf, 63, sizeof downsuf);     memset(up, -63, sizeof up);     memset(uppre, -63, sizeof uppre);     memset(upsuf, -63, sizeof upsuf);     int n;     cin >> n;     for (int i = 0; i < n; i++) cin >> p[i].first >> p[i].second;     for (int i = 0; i < n; i++) {       int x = p[i].first + p[i].second + N;       int y = p[i].first - p[i].second + N;       up[x] = max(up[x], y);       down[x] = min(down[x], y);     }     for (int i = 0; i < MAXN; i++) uppre[i] = upsuf[i] = up[i];     for (int i = 0; i < MAXN; i++) downpre[i] = downsuf[i] = down[i];     for (int i = 0; i < MAXN - 2; i++) {       uppre[i + 2] = max(uppre[i + 2], uppre[i]);       downpre[i + 2] = min(downpre[i + 2], downpre[i]);     }     for (int i = MAXN - 1; i > 1; i--) {       upsuf[i - 2] = max(upsuf[i], upsuf[i - 2]);       downsuf[i - 2] = min(downsuf[i - 2], downsuf[i]);     }     for (int i = 0; i < MAXN; i++)       down[i] = max((i - 1 > -1 && i - 1 < MAXN ? downpre[i - 1] : -1e9 - 7),                     (i + 1 > -1 && i + 1 < MAXN ? downsuf[i + 1] : -1e9 - 7));     for (int i = 0; i < MAXN; i++)       up[i] = min((i - 1 > -1 && i - 1 < MAXN ? uppre[i - 1] : 1e9 + 7),                   (i + 1 > -1 && i + 1 < MAXN ? upsuf[i + 1] : 1e9 + 7));     long long ans = 0;     for (int i = 1; i < MAXN - 1; i++) {       ans += max(0, up[i] - down[i]) / 2;     }     cout << ans << endl;     return 0;   }   