def has_prefix(sub_s, d):
	"""
	:param sub_s: (str) A substring that is constructed by neighboring letters on a 4x4 square grid
	:param d: (dict) A dictionary stores all the words which are at least 4 words
	:return: (bool) If there is any words with prefix stored in sub_s
	"""
	words_lst = d[sub_s[0]]
	if sub_s in words_lst:
		return True
	for word in words_lst:
		if word.startswith(sub_s) is True:
			return True
	return False