# include<iostream> # include<cstring> # include<cmath> 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]; } } for(int i=0;i<n;i++){ for(int j=0;j<n;j++) if(i==j) sum+=a[i][j]; } cout<<sum<<endl; return 0; }