using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string convert = "4+18/(9-3)";

​

        MatchCollection parts = Regex.Matches(convert, @"([\d\.]+|[()e^/%x*+-])");

        foreach(Match p in parts)

            Console.WriteLine("\"" + p.Value + "\"");

    }

}