#include <iostream>
using namespace std;

int main() {
    int n;
    int input;
    cin >> n;
    int **Graph = (int**)malloc(n*sizeof(int*));
    for (int i = 0; i < n; i++) {
        Graph[i] = (int*)malloc(n*sizeof(int));
    }

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> input;
            Graph[i][j] = input;
        }
    }
    int sum = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            sum += Graph[i][j];
        }
    }

    cout << sum/2;
    return 0;
}