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

class A
{
	static void Main()
	{
		int[] xs = Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();

		Array.Sort(xs);
		Console.WriteLine(string.Format("{0:f2}\n", (xs[1] + xs[2] + xs[3] + xs[4]) / 4.0));
	}
}