# include<iostream> using namespace std; int main(){ int n,sum=0; cin>>n; int a[n][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; }