# Validating Roman Numerals

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#
#   You are given a string, and you have to validate whether it's a valid Roman numeral. If it is valid, print True.
#   Otherwise, print False. Try to create a regular expression for a valid Roman numeral.
#
#   Input Format
#   A single line of input containing a string of Roman characters.
#
#   Output Format
#   Output a single line containing True or False according to the instructions above.
#
#   Constraints
#
#   The number will be between 1 and 3999 (both included).
#
#   Sample Input
#   CDXXI
#
#   Sample Output
#   True
#
#   References
#   Regular expressions are a key concept in any programming language. A quick explanation with Python examples is
#   available here. You could also go through the link below to read more about regular expressions in Python.
#   https://developers.google.com/edu/python/regular-expressions
#
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