def define_explore_range(num):
	"""
	Define a list of affiliated index with the current index for the further exploring.
	:param num: int, Current index in the letters list.
	:return: list[int], A list of all affiliated index for the further exploring.
	"""
	if num % 4 == 0:
		explore_lst = [num - 4, num - 3, num + 1, num + 4, num + 5]
	elif num % 4 == 3:
		explore_lst = [num - 5, num - 4, num - 1, num + 3, num + 4]
	else:
		explore_lst = [num - 5, num - 4, num - 3, num - 1, num + 1, num + 3, num + 4, num + 5]
	return explore_lst