#include<iostream>
using namespace std;
int main(){
    int n;
    cin>>n;
    
    double grade,sum=0;
    
    for(int i=0;i<n;i++);
      cin >> grade;
      
      if(grade < 0){
          
          cout<<"Invalid input";
          return 0;
      }
     sum += grade;
}
double gpa = sum/n;

cout<<gpa;

return 0;
}