#include<iostream> using namespace std; int main(){ int a[101][101],n,i,j,sum=0; cin>>n; int b=n/2+1; for(int i=1;i<=n;i++){ for(int j=1;j<=n;j++){ cin>>a[i][j]; if(i==j || i+j==n+1) sum+=a[i][j]; } } if(n%2!=0) sum-=a[b][b]; cout<<sum; return 0; }