using System;

public class Program

{

    public static void Main()

    {

        double sum = 0;

        for (int i =0; i < 5; i ++)

        {

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

            if (sum<= 0 && sum <=20)

            {

             sum + sum + number;

            }

            else

            {

                Console.WriteLine("Chisloto trqbva da e mejdu 0 i 20");

            }

        }

    }   sum = Math.Sqrt(sum);

        Console.WriteLine(sum);

}