Hi, here's your problem today. This problem was recently asked by Twitter:

Given a Roman numeral, find the corresponding decimal value. Inputs will be between 1 and 3999.

Example:
Input: IX
Output: 9

Input: VII
Output: 7

Input: MCMIV
Output: 1904
Roman numerals are based on the following symbols:
<pre>
I     1
IV    4
V     5
IX    9 
X     10
XL    40
L     50
XC    90
C     100
CD    400
D     500
CM    900
M     1000
</pre>
Numbers are strings of these symbols in descending order. In some cases, subtractive notation is used to avoid repeated characters. The rules are as follows:
1.) I placed before V or X is one less, so 4 = IV (one less than 5), and 9 is IX (one less than 10)
2.) X placed before L or C indicates ten less, so 40 is XL (10 less than 50) and 90 is XC (10 less than 100).
3.) C placed before D or M indicates 100 less, so 400 is CD (100 less than 500), and 900 is CM (100 less than 1000).

<pre lang=py>
class Solution():
  def romanToInt(self, s):
    # Fill this in.
    
n = 'MCMX'
print(Solution().romanToInt(n))
# 1910
</pre>