#include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     int n;     cin >> n;     int ans = 0;     for (int i = 0; i < n; ++i)       for (int j = 0; j < n; ++j) {         int inp;         cin >> inp;         if (i == j || i + j == n - 1 || i == n / 2 || j == n / 2) ans += inp;       }     cout << ans << endl;     return 0;   }   