// editor1
#include <iostream>
using namespace std;

int main(){
    int n;
    cin>>n;
    
    if(n<1 || n>10){
        cout<<"Invalid input";
        return 0;
    }
    
    float grade, sum = 0;
    
    for(int i=0; i<n; i++){
        cin>>grade;
        
        if(grade < -10 || grade>10){
            cout>>"Invalid input";
            return 0;
        }
        if(grade<0){
            cout<<"Invalid input";
            return 0;
        }
        sum+=grade;
    }
    cout<<sum/n;
    return 0;
}