using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string s = "[1]Ali ahmadi,[2]Mohammad Razavi";
		Regex regex = new Regex(@"\[(\d+)\]", RegexOptions.Compiled);
	        foreach (Match match in regex.Matches(s))
            	{
			Console.WriteLine(match.Groups[1].Value);
		}
	}
}