#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
}