using System;
using System.Linq;

public class Program
{
	public static void Main()
	{
		int[] scores = Console.ReadLine().Split().Select(i => int.Parse(i))
			.OrderBy(i => i).ToArray();
		
		double sum = 0.0;
		for (int i = 1; i < 5; i++)
		{
			sum += scores[i];
		}
		Console.WriteLine("{0:##0.00}", sum / 4);
	}
}