using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static string solution(string s)

    {

        string digits = new String(s.Where(Char.IsDigit).ToArray());

        int count = digits.Length;

        int temp = 0;

        List<string> l = new List<string>();

        while (count != temp)

        {

            if (count - temp == 4 || count - temp == 2 || count == 2)

            {

                l.Add(digits.Substring(temp, 2));

                temp = temp + 2;

            }

            else

            {

                l.Add(digits.Substring(temp, 3));

                temp = temp + 3;

            }

        }

​

        return String.Join("-",l);

    }

​

    public static void Main()

    {

        string m=solution("12#45@6789");

        Console.WriteLine(m);

    }

}