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

}