using System;

using System.Text.RegularExpressions;

using System.Linq;

public class Program

{

    public static void Main()

    {

         var ifcUsers = Regex.Matches(

                    "2304923,121782781,ALMUFTIO:123912,OSIENA:129038", "\\d+")

                   .Cast<Match>()

                   .Select(m => m.Value)

                   .ToList();

        foreach(string u in ifcUsers) {

                Console.WriteLine(u);

        }

    }

}