#include<iostream>
using namespace std;

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