#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 i=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;
}
}