#include<iostream> #include<cstdio> using namespace std; int a[10][10]; int main(){ int n; int 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 == n-1||i==j){ sum += a[i][j]; } } } cout<<sum; return 0; }