using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        string pattern =  @"H";

        string input = "Hello World!";

        Regex regex = new Regex(pattern);

        Match match = regex.Match(input);

        if (match.Success)

        {

            Console.WriteLine($"{match.Value} found");

        }

        else

        {

            Console.WriteLine("No match found.");

        }

    }

}