#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 0;
}