Kaspichan_Numbers

using System;

class KaspichanNumbers
{
    const int Base = 256;
    static char[] startingLetter = { '\0', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i' };

    static string ConvertToKaspichan(ulong remainder)
    {
        string kaspichanNum = null;
        ulong rem = remainder % 26;
        ulong div = remainder / 26;
        char first = (char)(rem + 65);
        kaspichanNum += first.ToString();
        if (div != 0)
        {
            for (int i = 1; i < startingLetter.Length; i++)
            {
                if (div == (ulong)i)
                {
                    kaspichanNum += startingLetter[i].ToString();
                    break;
                }
            }
        }
        return kaspichanNum;
    }
    static void Main()
    {
        ulong number = ulong.Parse(Console.ReadLine());
        string kaspichan = null;

        while (true)
        {
            ulong remainder = number % Base;
            ulong division = number / Base;

            // convert remainder to kaspichan
            kaspichan += ConvertToKaspichan(remainder);

            if (division == 0)
            {
                break;
            }
            if (division < Base)
            {
                kaspichan += ConvertToKaspichan(division);
                break;
            }
            else
            {
                number /= Base;
            }
        }
        for (int i = kaspichan.Length - 1; i >= 0; i--)
        {
            Console.Write("{0}", kaspichan[i]);
        }
        Console.WriteLine();
    }
}