#include<iostream>
#include<vector>
#include<numeric>
#include<cstdlib>
using namespace std;
const int MIN_GRADE=-10;
const int MAX_GRADE=10;
int main(){
    int n;
    if(!(cin>>n)){
        cout<<"Invalid input"<<endl;
        exit(1);
    }
    int sum_of_grades=0
    int grades;
    for(int i=0;i<n;i++){
        if(!(cin>>grades)){
            cout<<"Invalid input"<<endl;
            exit(1);
        }
        if(grades<MIN_GRADE || grades > MAX_GRADE){
            cout<<"Invalid input"<<endl;
            exit(1);
        }
        sum_of_grades+=grades;
    }
    float gpa =static_cast<float>(sum_of_grades)/n;
    cout<<gpa<<endl;
    return 0;
}