#include<iostream> using namespace std; int main() { int n; cin >> n; int matrix[n][n]; int sum = 0; for (int i = 0; i < n; i++) { for (int j = 0; j < n; j++) { cin >> matrix[i][j]; if (i == j) { sum += matrix[i][j]; } } } cout <<sum << endl; return 0; }