#include<bits/stdc++.h> using namespace std; int a[10][10]; int main(){ int n,x = 0; cin>>n; for (int i = 0;i <= n - 1;i++){ for (int j = 0;j <= n - 1;j++){ cin>>a[i][j]; } } for (int i = 0;i <= n - 1;i++){ for (int j = 0;j <= n - 1;j++){ if (i == j || i + j == n - 1){ x += a[i][j]; } } cout<<endl; } cout<<x; return 0; }