#include<iostream> using namespace std; int main() { int n, sum = 0; cin >> n; int a[n][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { cin >> a[i][j]; } } for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { if (i == j) sum = sum + a[i][j]; else if (j + i == n - 1) sum += a[i][j]; } } cout << sum; return 0; }