using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string pattern1 = @"[a-z._0-9]+@[a-z0-9]+.\w{3}";

        string input1 = @"this is jessikachrustel@gial.com sttudying in ku";

        string pattern2 = @"\w{4}://+[a-z._0-9]+.\w{3}|\w{3}.+[a-z._0-9]+.\w{3}";

        string input2= @"the url http://dotnet.net

        http://mail.google.com    www.karunya.edu";

        string pattern3 = @"[a-z\w{2}[a-z]+\d{3}|\d{4}";

        string input3= @"ur14cs251 ur14cs249 pr14cs2004 pr15cs2435";

        MatchCollection mc1= Regex.Matches(input1, pattern1);

        foreach(Match m1 in mc1)

        {

            Console.WriteLine("the @gmail is given by :{0} " , m1.Value);

        }

        MatchCollection mc2= Regex.Matches(input2, pattern2);

        foreach(Match m2 in mc2)

        {

            Console.WriteLine("the url :{0} " , m2.Value);

        }

        MatchCollection mc3= Regex.Matches(input3, pattern3);

        foreach(Match m3 in mc3)

        {

            Console.WriteLine("the registernumber  :{0} " , m3.Value);

        }

    }

}