#include<iostream> using namespace std; int a[100][100]; int main(){ int n,sum = 0; cin >> n; for(int i = 0;i < n;i++){ for(int j = 0;j < n;j++){ cin >> a[i][j]; if(i == j || i+j ==n-1){ sum +=a[i][j]; } } } cout << sum; return 0; }