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