using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = "29/10/2018 14:50:09402325 671";

        Regex rx = new Regex(@"(.*):([^:]+)",

          RegexOptions.Compiled | RegexOptions.IgnoreCase);

        MatchCollection matches = rx.Matches(input);

        if ( matches.Count >= 1 ) {

            var m = matches[0].Groups;

            Console.WriteLine(m[1]);

            Console.WriteLine(m[2]);    

        }

    }

}