#include<bits/stdc++.h> 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 sum=0; for (int i=0;i<n;i++){ sum=sum+a[i][i]+a[i][n-1-i]; } if (n%2==1){ sum=sum-a[n/2][n/2]; } cout<<sum; return 0; }