#15 - Дороги [+]

#include <iostream>
#include <cstdio>
#include <math.h>
using namespace std;
int main() {
    // insert code here...
    freopen("INPUT.txt", "r", stdin);
    freopen("OUTPUT.txt", "w", stdout);
    int n;
    int a[1000][1000];
    int count;
    cin>>n;
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            cin>>a[i][j];
            if (a[i][j] == 1) {
                count++;
            }
        }
    }
    cout<<count/2<<endl;
    return 0;
}