import re


def get_file_number(filename):
	"""
	Get the number of the current decow corpus part.

	Args:
		filename (str): Decow corpus part file name

	Returns:
		str: File number
	"""
	file_n = re.findall(re.compile("\d{2}(?=[^a])"), filename)  # Retrieve file number
	if len(file_n) == 0:
		file_n = re.findall(re.compile("\d+"), filename)[len(file_n) - 1]
	else:
		file_n = file_n[len(file_n) - 1]
	return file_n if int(file_n) > 9 else "0" + file_n