using System;

using System.Linq;

using System.Collections.Generic;

using System.Text;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        var testCases = new List<string>

        {

@"*D$$$ADH**D$$$7ZJ**D$$$7ZI*",

    @"*D$$$ADH*

    *D$$$7ZJ*

    *D$$$7ZI*",

@"*D$$$ADH*

*D$$$7ZJ*

*D$$$7ZI*",

@"*D$$$ADH*                     *D$$$7ZJ*  *D$$$7ZI*",

@"$$29N6                     *D$$$7ZJ*  *D$$$7ZI*",

@"$$29N6    JKKKKKKKKKKKKHJH          sdfsdfsf *ASDFER*           *D$$$7ZJ*  *D$$$7ZI*",

        };

        foreach (var test in testCases)

        {       

            string result = CleanUpScanInput(test);

            Console.WriteLine("Wejście:");

            Console.WriteLine(test);

            if (string.Equals(test.TrimEnd(), result.TrimEnd(), StringComparison.Ordinal))

            {

               Console.WriteLine(" -- Wynik bez zmian -- ");

            }

            else

            {

                Console.WriteLine("Wynik:");

                Console.WriteLine(result);

            }

​

            Console.WriteLine("-------------------");

        }

    }

    private static string CleanUpScanInput(string source)

    {

      string result = source

        .Replace("**", "* *")

        .Replace("\n", " ")

        .Replace("\r", " ")

        .Replace("\t", " ")

        .RemoveMultipleWhiteSpaces()

        .Split(' ')

        .Select(i => i.Trim().Trim(new[] { '*' }))

        .Select(i => 6 <= i.Length && i.Length <= 7 && i.All(j => char.IsUpper(j) || char.IsDigit(j) || j == '$') ? $"*{i}*" : i)

        .Join(Environment.NewLine);

​

      return result + Environment.NewLine;

    }

}

​

public static class StringExtensions

{

    private static readonly Regex _multipleSpaces = new Regex(@" {2,}", RegexOptions.Compiled);

    public static string CondenseSpaces(this string s)

    {

        return s.Aggregate(new StringBuilder(), (acc, c) =>

        {

            if (!char.IsWhiteSpace(c) || c == '\r' || c == '\n' || acc.Length == 0 || acc[acc.Length - 1] != ' ')

                acc.Append(c);

            return acc;

        }).ToString();

    }

​

    public static bool HasValue(this string value) => !string.IsNullOrWhiteSpace(value);

​

    public static bool IsNullOrWhiteSpace(this string value) => string.IsNullOrWhiteSpace(value);

    public static string Join(this IEnumerable<string> @values, string separator) => string.Join(separator, @values);

    public static string RemoveMultipleNewLines(this string value) => value.Split(new[] { "\r\n" }, StringSplitOptions.None).Where(l => !l.IsNullOrWhiteSpace()).Join("\r\n");

​

    public static string RemoveMultipleWhiteSpaces(this string value) => _multipleSpaces.Replace(value, " ");

    public static string RemoveCharacters(this string value, Func<char, bool> predicate) => value is null ? null : new string(value.Where(c => !predicate(c)).ToArray());

}