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

int main() {
  int N;
  cin >> N;
  
  vector<double> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
 
  sort(v.begin(), v.end());
  
  double avg = 0.0;
  for (int i = 0; i < N-1; i++) {
    if (i==0) avg = (v[i] + v[i+1])/2;
    else avg = (avg + v[i+1])/2;
  }
  
  cout << avg << endl;
  
}