#include<iostream>
using namespace std;
int amin()
{
    int n;
    cin >> n;
    float grade,sum = 0;
    for(int i = 0; i<n; i++){
        cin>> grade;
        if(grade<0){
            cout<<"Invalid input";
            return 0;
        }
        sum =+ grade;
    }
    cout << sum / n;
    return 0;
}