#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
    int num;
    cin>>num;
    try
    {
        if(num<1||num>10)
        {
            throw"Invalid input";
        }
        double grade;
        double total=0;
        for(int i=0;i<num;i++)
        {
            cin>>grade;
            if(grade<0)
            
        
        {
        
            throw"Invalid input";
        
        }
        total+=grade;
        }
         double gpa =total/num;
         cout<<gpa;
    }
    catch(const char* msg)
    {
        cout<<msg<endl;
    }
    return 0;

}