#include<iostream> 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 l = 0; for (int i = 0; i < n; i++) { l = l + a[i][i] + a[i][n - 1 - i]; } if(n%2==1){ l=l-a[n/2][n/2]; } cout << l; return 0; }