def check_input_format(input_data):
	"""
	check if the input data is numbers > 0.
	:param input_data: str, the input number of row runs to achieved.
	:return: str, the data in legal format.
	"""
	while not input_data.isdigit() or int(input_data) <= 0:
		input_data = input("Illegal format, please enter numbers > 0: ")
	return input_data