#include <iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    if(n<=0){
        cout<<"Invalid input";
        return 0;
    }
    double grade sum=0;
    for(int i=0;i<n;i++){
        cin>>grade;
        if(grade<0){
            cout<<"Invalid input";
            return 0;
        }
        sum+=grade;
    }
    double gpa=sum/n;
    cout<<gpa;
    return 0;
}