using System;
class gyakusu{
  public static void Main(){
    int n = int.Parse(Console.ReadLine());
    string[] s =  Console.ReadLine().Split(' ');
    Array.Sort(s);
    double sum = double.Parse(s[0]);
    for (int i = 0; i<n-1; i++)
    {
      double tmp1 = double.Parse(s[i]);
      double tmp2 = double.Parse(s[i+1]);
      double tmp3 = (tmp1+tmp2)/ 2;
      s[i+1] = tmp3.ToString();
  }
  Console.WriteLine("{0:F5}",s[n-1]);
}
}