using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using static System.Console;
using static System.Math;


namespace AtCoder
{
    class AtCoderrr
    {
        static void Main(string[] args)
        {
            int n = int.Parse(ReadLine());
            double[] s = ReadLine().Split(' ').Select(double.Parse).ToArray();
            var ls = new List<double>();
            double ans = 0;
            ls.AddRange(s);
            ls.Sort();
            for (int i = 0; i < n-1; i++)
            {
                ls.Add(Func(ls[0], ls[1]));
                ls.Remove(ls[0]);
                ls.Remove(ls[0]);
            }
            WriteLine(ls[0]);
        }

        static double Func(double x,double y)
        {
            return (x + y) / 2;
        }
    }
}
