#include<iostream>
using namespace std;

class statistics{
    private:
    double mean;
    public:
    statistics(int arr[],int n){
        if(n<=o){
            mean=-1;
            return;
        }
        int sum =0;
        for(int i=0;i<n;i++){
            sum+=arr[i];
        }
        mean=(double)sum/n;
    }
    statistics(const Statistics &obj)
    {
        mean=obj.mean;
    }
    void display(){
        if (mean==-1)
        cout<<"Invalid input";
        else 
        cout<<mean;
    }
};
int main(){
    int n;
    cin>>n;
    if (n<0){
        cout<<"Invalid input";
        return 0;
    }
    int arr[n];
    for (int i=0;i<n;i++){
        cin>>arr[i];
    }
    statistics obj1 (arr,n);
    statistics obj2=obj1;
    obj2.display();
    return 0;
}