using System;
using System.Text.RegularExpressions;
 
namespace RegExApplication
{
   public class Program
   {
      public static void Main(string[] args)
      {
         string input = "x-[ABCD]";
         string pattern = "^x-\\[(.*)\\]$";
         Regex rgx = new Regex(pattern);
         
         Match match = rgx.Match(input);

        	if (match.Success)
        	{
            	Console.WriteLine(match.Groups[1].Value);
        	}
      }
   }
}