money separator // not regex

using System;
using System.IO;
using System.Xml;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main()
    {
        string numb;

        do
        {

            Console.WriteLine("Enter input: ");

            numb = Console.ReadLine();

            Console.WriteLine("Format input: " + sepMoney(int.Parse(numb)));
            Console.WriteLine();
            Console.WriteLine();
        }
        while (numb != "666");
    }

    private static string sepMoney(int numb)
    {
        char sepChar = ',';
        string money = "";

        int sepAmount = 1000;

        while ((numb % sepAmount) > 100)
        {
            money = string.Format("{1}{2}{0}", money, numb % sepAmount, sepChar);
            numb = numb / sepAmount;
        }

        if (numb > 0)
            money = string.Format("{0}{2}{1}", numb, money, sepChar);

        if (money[money.Length - 1] == sepChar)
            money = money.Substring(0, money.Length - 1);

        return money;
    }
}