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