#include <bits/stdc++.h>
#include <algorithm>
#include <iostream>
using namespace std;

int main(){
  
  int N;
  cin >> N;

  vector<int> v(N);
  for(int i=0; i<N; i++;){
    v.at(i);
  }
  
  double ANS = 0;
  
  stable_sort(v.begin(), v.end());
  
  ANS = (v.at(0) + v.at(1))/2;
  
  for(int i=2; i<N; i++){
    ANS += (ANS + v.at(i))/2;
  }
  
  cout << ANS << endl;
}