using System;

using System.Collections.Concurrent;

public class Program

{

    public static void Main()

    {

        var dictionary = new ConcurrentDictionary<string, string>();

        dictionary[";ra"] = "three";

        Console.WriteLine("Hello World: " + dictionary[";ra"]);

        dictionary[";ra"] = "threePointSomething";

        Console.WriteLine("Hello World: " + dictionary[";ra"]);

        dictionary["ra!@"] = "four";

        Console.WriteLine("Hello World: " + dictionary["ra!@"]);

    }

}