#include <iostream>
using namespace std;

int main(){
    int n;
    cin>>n;
    
    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;
}