#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;
}