#include<iostream>
using namespace std;
class statistics {
    float mean;
    public:
    statistics(int arr[],int n){
        if (n<=0){
            mean = -1;
            return;
        }
        int sum =0;
        for (int i=0; i<n; i++){
            sum +=arr[i];
        }
        mean =(float)sum/n;
    }
    statistics(const statistic & 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[100];
    
    for (int i = 0; i<n ;i++){
        cin>> arr[i];
    }
    statistics s1(arr,n);
    statistics s2=s1;
    s2.display();
    return 0;
}