// editor1
#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 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;n++){
        cin>>arr[i];
    }
    statistics s1(arr,n);
    statistics s2 = s1;
    s2.display();
    return 0;
}