using System;
using System.Linq;
using System.Collections.Generic;

using E = System.Linq.Enumerable;

public class Program
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine());
        var seqV = Console.ReadLine().Split().Select(x => double.Parse(x)).ToArray();

        var materials = new SortedSet<double>(seqV);
        while (materials.Skip(1).Any())
        {
            var x = materials.Min;
            materials.Remove(x);
            var y = materials.Min;
            materials.Remove(y);

            materials.Add((x + y) / 2);
        }
        Console.WriteLine(materials.Min);
    }
}
