using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var input = "Hello World!";
		var keyword = "Hello";
		var result = Regex.Replace(input, Regex.Escape(keyword), "<b>$&</b>");
		Console.WriteLine(result);
	}
}