using System;
using System.Collections.Generic;
using System.Diagnostics.Eventing.Reader;
using System.Linq;

class Progaram
{
    static void Main(string[] args)
    {
        var N = int.Parse(Console.ReadLine());
        var vs = Console.ReadLine().Split(' ')
            .Select(x => double.Parse(x)).ToList();
        vs = vs.OrderBy(x => x).ToList();
        while (vs.Count != 1)
        {
            for (var i = 0; vs.Count - 1 > i; i++)
            {
                vs.Add((vs[i] + vs[i + 1]) / 2.0);
                vs.RemoveAt(i);
                vs.RemoveAt(i);
            }
            vs = vs.OrderBy(x => x).ToList();
        }
        Console.WriteLine(vs[0]);
    }
}
