#include<iostream>
using namespace std;
class statics{
    float mean;
    public;
    statics(int arr[],int n){
        if(n<=0){
            mean=-1;
            return Invalid;
        }
        int sum=0;
        for(int i=0;i<n;i++){
            sum+=arr[i]
        }
        mean=(float)sum/n;
    }
    static(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[i];
    }
    statics s1(arr,n);
    statics s2=s1;
    s2 display();
    return 0;
}