using System;

using System.Collections.Generic;

using System.Threading;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Reverse("Hello World!"));

    }

    private static string Reverse(string text)

    {

        var chars = text.ToCharArray();

        var newChars = new char[chars.Length];

        var threads = new List<Thread>();

        for (var i = 0; i < chars.Length; i++)

        {

            var thread = new Thread(x => newChars[newChars.Length - x - 1] = chars[(int)x]);

            thread.Start(i);

            threads.Add(thread);

        }

        foreach (var thread in threads)

            thread.Join();

        return new string(newChars);

    }

}