def is_legal_input(row):
	"""
	:param row: (string) input string from user
	:return: (boolean) if legal input
	"""
	# check if over 4 char
	if len(row.split()) != 4:
		print('Illegal input')
		return False
	# check if each element only one character
	else:
		for char in row.split():
			if len(char) != 1:
				print('Illegal input')
				return False
		return True