using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(ObfuscateUserId(50018));

    }

    public static string ObfuscateUserId(int IdUser)

    {

        char[] charArray = IdUser.ToString("X").ToCharArray();

        Array.Reverse(charArray);

        return new string(charArray);

    }

}