using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
		// your code goes here
		
		int n = int.Parse(Console.ReadLine());
		var v = Console.ReadLine().Split().Select(x => double.Parse(x)).ToArray();
		Array.Sort(v);
		double ans = ( v[0] + v[1] )/2;
		
		for(int i=2; i>n; i++){
			ans = ( v[i] + ans )/2;
		}
		
		Console.WriteLine(ans);
		
	}
}