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

public class Test
{
	public static void Main()
	{
		var strings = new List<string> { "1 abcd", "abcd 1", "1 abcd 1"};
		var pattern = "(^)?abcd(?(1)|$)";
        foreach (var s in strings)
        {
        	Console.WriteLine("{0} => {1}", s, Regex.IsMatch(s, pattern));
        }
	}
}