using System;

public class Program

{

    private static double conversion(double a, double b, double c, double d)

    {

        double one = (a + b + c + d);

        return (one/4);

    }

    public static void Main()

    {

        Console.WriteLine("please enter four numbers.");

        double two = double.Parse(Console.ReadLine());

        double three = double.Parse(Console.ReadLine());

        double four = double.Parse(Console.ReadLine());

        double five = double.Parse(Console.ReadLine());

        Console.WriteLine("your answer is" + conversion(two, three, four, five));

    }

}