#!/usr/bin/env pythonimport reimport sys# case of catastrophic backtracking in Python## regex: (a*)*b# strings: aa...a## call with timing as:## > time ./catastrophic.py 20# counter n given on the command linecn = sys.argv[1]# calling the matching functions = ("a" * int(cn))m = re.match('(a*)*b' , s) print s