#include<bits/stdc++.h>
using namespace std ;
int main () {
  
  int N 
  cin >> n;
  double a[N] ;
  for(int i =0 ; i < N ;i++)
    cin >> a[i] ;
  sort(a,a+N) ;
  double curr= (a[0] + a[1])/2 ;
  for(int i = 2 ; i <  N; i++)
    curr = (curr + a[i])/2 ;
  cout<<curr<<endl;
 
  
  
  return 0 ;
  
} 