using System;
using static System.Console;
using static System.Math;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace atcoder
{
    class Program
    {
        //メイン関数
        static void Main(string[] args)
        {
            int N = ReadI();
            var u = Read().Split(' ').Select(x => int.Parse(x)).ToArray();

            float ans = 0.0f;

            u.OrderBy(x => x);

            for (int i = 1; i < N; i++)
            {
                if (i == 1)
                {
                    ans = (u[i - 1] + u[i]) / 2.0f;
                }
                else ans = (ans + u[i]) / 2.0f;

            }

            Write(ans);
            ReadKey();
        }

        //メインじゃない関数
        private static string Read() { return ReadLine(); }
        private static int ReadI() { return int.Parse(ReadLine()); }
    }
}
