





def lowerCAmelCase__(__snake_case							)				->      bool:







	'''simple docstring'''







	return credit_card_number.startswith(('''34''', '''35''', '''37''', '''4''', '''5''', '''6''')							)





def lowerCAmelCase__(__snake_case							)				->      bool:







	'''simple docstring'''







	lowerCamelCase__								=		credit_card_number
	lowerCamelCase__								=		0
	lowerCamelCase__								=		len(__snake_case							) - 2
	for i in range(__snake_case       ,-1       ,-2							):
		#  double the value of every second digit
		lowerCamelCase__								=		int(cc_number[i]							)
		digit *= 2
		# If doubling of a number results in a two digit number
		# i.e greater than 9(e.g., 6 × 2 = 12),
		# then add the digits of the product (e.g., 12: 1 + 2 = 3, 15: 1 + 5 = 6),
		# to get a single digit number.
		if digit > 9:
			digit %= 10
			digit += 1
		lowerCamelCase__								=		cc_number[:i] + str(__snake_case							) + cc_number[i + 1 :]
		total += digit

	# Sum up the remaining digits
	for i in range(len(__snake_case							) - 1       ,-1       ,-2							):
		total += int(cc_number[i]							)

	return total % 10 == 0





def lowerCAmelCase__(__snake_case							)				->      bool:







	'''simple docstring'''







	lowerCamelCase__								=		F'{credit_card_number} is an invalid credit card number because'
	if not credit_card_number.isdigit():
		print(F'{error_message} it has nonnumerical characters.'							)
		return False

	if not 13 <= len(__snake_case							) <= 16:
		print(F'{error_message} of its length.'							)
		return False

	if not validate_initial_digits(__snake_case							):
		print(F'{error_message} of its first two digits.'							)
		return False

	if not luhn_validation(__snake_case							):
		print(F'{error_message} it fails the Luhn check.'							)
		return False

	print(F'{credit_card_number} is a valid credit card number.'							)
	return True


if __name__ == "__main__":
			import doctest

			doctest.testmod()
			validate_credit_card_number("4111111111111111")
			validate_credit_card_number("32323")










def lowerCAmelCase__(__snake_case							)				->      str:







	'''simple docstring'''







	return "".join(chr(ord(__snake_case							) - 32							) if '''a''' <= char <= '''z''' else char for char in word							)


if __name__ == "__main__":
			from doctest import testmod

			testmod()



