#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    try{
        if(n<1 || n>10){
            throw"Invalid input";        }
    }
    double grade;
    double sum=0;
    for(int i=0;i<n;i++){
        cin>>grade;
        if(grade<0){
            throw"Invalid input";
        }
        sum+=grade;
    }
    double gpa=sum/n;
    cout<<gpa;
}
catch(const char* msg){
    cout<<msg;
}
return 0;
}