using System;
class bable{
  public static void Main(){
    int kosuu = int.Parse(Console.ReadLine());
    double[] value =new double[kosuu];
    string[] s = Console.ReadLine().Split(' ');
    for (int i = 0; i<kosuu; i++) {
      value[i] = double.Parse(s[i]);
    }
    double stb =0;
    for (int i=0; i<kosuu-1; i++) {
      for (int j=i;j<kosuu-1;j++){
        if (value[j]>value[j+1]) {
          stb = value[j];
          value[j] = value[j+1];
          value[j+1]=stb;
        }
      }
    }
     double sum = (value[0]+value[1])/2;
     for (int p=2; p<kosuu; p++) {
       sum = (sum+value[p])/2;
     }
      Console.WriteLine("{0}",sum);
    }

  }
