using System;
class gyakusu{
  public static void Main(){
    int n = int.Parse(Console.ReadLine());
    string[] s =  Console.ReadLine().Split(' ');
    Array.Sort(s);
    double[] a = new double[n];
    double[] inverse = new double[n];
    double sum = double.Parse(s[0]);
    for (int i = 1; i<n; i++)
    {
      sum = (sum+double.Parse(s[i]))/2;
  }
  Console.WriteLine("{0:F5}",sum);
}
}