I would like to give some feedback about wrong check result. I do try my code also on my shell, and can get the right answer for "3999". But your check result give me "MMMCMXCIX". I'm a beginner on writing code, so my code may be wrong. I'd like to know it is a bug or my fault.
From: http://www.checkio.org/mission/roman-numerals/solve/
HTTP_USER_AGENT:
Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.71 Safari/537.36
Created at: 2015/10/16 19:02; Updated at: 2015/10/16 20:04