Roman Numerals

Rules

Implement the ArabicToRoman method which takes a positive Arabic integer and returns the Roman Numeral as a string.

Example:

Roman numerals are expressed by letters of the alphabet:

I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000

A letter repeats its value that many times (XXX = 30, CC = 200, etc.). A letter can only be repeated three times.
If one or more letters are placed after another letter of greater value, add that amount.
If a letter is placed before another letter of greater value, subtract that amount.
1. Only subtract powers of ten (I, X, or C, but not V or L)
2. Only subtract one number from another.
3. Do not subtract a number from one that is more than 10 times greater (that is, you can subtract 1 from 10 [IX] but not 1 from 20—there is no such number as IXX.)