Integer to Roman

Problem

Given an integer, convert it to a roman numeral.

The number is guaranteed to be within the range from 1 to 3999.

Example

4 -> IV
12 -> XII
21 -> XXI
99 -> XCIX

More examples at: http://literacy.kent.edu/Minigrants/Cinci/romanchart.htm

Note

What is Roman Numeral?

• https://en.wikipedia.org/wiki/Roman_numerals
• https://zh.wikipedia.org/wiki/%E7%BD%97%E9%A9%AC%E6%95%B0%E5%AD%97
• http://baike.baidu.com/view/42061.htm