#!/usr/bin/env python3

import re

import sys

# case of catastrophic backtracking in Python

#

# regex: (a*)*b

# strings: aa...a

#

# call with timing as:

#

#   time ./catastrophic.python 20

# counter n given on the command line

cn = sys.argv[1]

# calling the matching function

s = ("a" * int(cn))

m = re.match('(a*)*b' , s) 

print(s)