#include<iostream>
#include<vector>
#include<iomanip>
using namespace std;

int main(){
    int n;
    if(!(cin>n)) return 0;
    double sum=0;
    double grade;
    bool isValid=true;
    for(int i=0;i<n;++i){
        if(!(cin>>grade)) break;
        if(garde<0){
            isValid =false;
            break;
        }
        sum+=garde;
    }
    if(!isValid){
        cout<<"Invalid input"<<endl;
    }
    else{
        double gpa=sum/n;
        cout<<gpa<<endl;
    }
    return 0;
}