#include<iostream>
#include<vector>

using namespace std;

void solve(){
    int n;
    if (!(cin >> n)) return;
    
    double sum = 0;
    double grade;
    bool isValid = true;
    
    for (int i = 0;i<n; ++i){
        cin >> grade;
        
        if (grade <0){
            isValid = false;
            break;
        }
        sum += grade;
    }
    if (!isValid) {
        cout << "Invalid input" << endl;
        else{
            
            double gpa = sum/n;
            cout << gpa << endl;
        }
    }
    int main() {
        solve();
        return 0;
    }