#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]; } cout << sum; return 0; }