#include<iostream>
using namespace std;

int main() {
    int n;
    cin >> n;
    
    try {
    
    if (n < 1 || n >10) {
        throw "invalid input";
        return 0;
    }
    
    double grade;
    double sum = 0;
    
    for (int i = 0; i < n; i++) {
        cin >> grade;
        
        if (grade < 0) {
            throw "invalid input";
            return 0;
        }
        
        sum += grade;
    }
    
    double gpa = sum / n;
    cout << gpa;
    }
    catch (cout char* msg) {
        cout << msg;
    }
    return 0