#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    try{
        if(n < 1|| n>10){cout<<"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;
}