using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("would you like to go from hex to denary(HD) or denary to hex(DH)");

        string Decision = Console.ReadLine();

        if (Decision == "DH")

        {

        Console.WriteLine("Please enter BinaryValue");

        string binaryNum = Console.ReadLine();

        int i = 0;

        string [] arrayNum = new string [binaryNum.Length];

        for(i = 0; i < binaryNum.Length; i++)

        {

               arrayNum[i] = binaryNum.Substring(i, 1);

        }

        for(i = 0; i < binaryNum.Length; i++) 

        {

            if((i+1)%4 == 0)

            {   

                string x = arrayNum[i-3] + arrayNum[i-2] + arrayNum[i-1] + arrayNum[i];     

                if (x == "0000")

                {

                    Console.Write(0);

                }

                if (x == "0001")

                {

                    Console.Write(1);

                }

                if (x == "0010")

                {

                    Console.Write(2);

                }

                if (x == "0011")

                {

                    Console.Write(3);

                }

                if (x == "0100")

                {

                    Console.Write(4);

                }

                if (x == "0101")

                {

                    Console.Write(5);

                }

                if (x == "0110")

                {

                    Console.Write(6);

                }

                if (x == "0111")

                {

                    Console.Write(7);

                }

                if (x == "1000")

                {

                    Console.Write(8);

                }

                if (x == "1001")

                {

                    Console.Write(9);

                }

                if (x == "1010")

                {

                    Console.Write("A");

                }

                if (x == "1011")

                {

                    Console.Write("B");

                }

                if (x == "1100")

                {

                    Console.Write("C");

                }

                if (x == "1101")

                {

                    Console.Write("D");

                }

                if (x == "1110")

                {

                    Console.Write("E");

                }

                if (x == "1111")

                {

                    Console.Write("F");

                }                  

            }               

          }     

         if (Decision == "HD")

         {

         }

      }

   }        

}