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