#include<bits/stdc++.h> using namespace std; int main() { int n; cin >> n; int a[n][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { cin >> a[i][j]; } } int sum = 0; for (int i = 0; i < n; i++) { sum = sum + a[i][i] + a[i][n - 1 - i]; } if (n % 2 == 1) { sum = sum - a[n / 2][n / 2]; } cout << sum; return 0; }