varianta88_II_5

#include <iostream>
using namespace std;
int a[21][21];
int main()
{
    int i,j,n,m=0,nr=0;
    cin>>n;
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=n;j++)
        {
            cin>>a[i][j];
            if(i<j && a[i][j]>0)
            {
                m+=a[i][j];
                nr++;
            }
        }
    }
    if(nr!=0)
    {
        cout<<(double) m/nr;
    }
    else
    {
        cout<<"NU EXISTA";
    }
    return 0;
}