#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    try{
        if(n<1 || n>10){
            throw"Invalid input";
        }
        double gared,sum=0;
    }
    for(int i=0; i<n; i++){
        cin>>grade;
        if (grade<0){
            throw"Invadid input";
        }
        sum+=grade;
    }
    double gpa =sum/n;
    cout<<gpa;
}
catch(const char* a)
{
    cout<<a;
}