#include<iostream> using namespace std; int main(){ short a,c=0,i,j; cin>>a; short b[a][a]; for(i=0;i<a;i++){ for(j=0;j<a;j++) { cin>>b[i][j]; } } for(i=0;i<a;i++){ for(j=0;j<a;j++){ if(i==j||i+j==a-1) { if(i==j&&i+j==a-1) continue; c+=b[i][j]; } } } cout<<c; return 0; }