#include<bits/stdc++.h> using namespace std; long long a[1005][1005]; int main(){ int n,sum=0; cin>>n; for(int i=1;i<=n;i++){ for(int j=1;j<=n;j++){ cin>>a[i][j]; if(i==j) sum+=a[i][j]; if(i+j==n+1) sum+=a[i][j]; } } if(n%2==0) cout<<sum; else{ sum=sum-a[n/2+1][n/2+1]; cout<<sum; } return 0; }