#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    try{
        if(n < 1 || n > 10){
            throw "Invalid input";
        }
        double grade, sum = 0;
        for(int 1 = 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;
    }
    return 0;
}