#include<iostream>
using namespace std;
int main()
{
    int n;
    cin >> n;
    try{
        if(n < 1 || n > 10){
            throw"Invalid input";        }
    }
    double gread , sum =0;
    for(int i = 0; i<n; i++)
    {
        cin>>grade;
        if(grade<0){
            throw"Invalid input";
        }
        sum += grade;
    }
    double gpa = sum/n;
    cout<<gpa;}
    catch(const char*a)
    {
        cout<<a;
    }
}