#include<iostream>
using namespace std;

int main()
{
    int n;
    cin >> n;
    try
    {
        if(n < 1|| n > 10)
        {
            throw "Invalid input";
        }
        double grade;
        double 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*msg)
    {
        cout << msg;
    }
    return 0;
}