
def 
(letters):
	""" find_words from scrabble transformation to 
	recursive """
	results = set()
	for a in letters:
		if a in WORDS: results.add(a)
		if a not in PREFIXES: continue
		for b in removed(letters, a):
			w = a + b
			if w in WORDS: results.add(w)
			if w not in PREFIXES: continue
			for c in removed(letters, w):
				w = a + b + c
				if w in WORDS: results.add(w)
				if w not in PREFIXES: continue
				for d in removed(letters, w)
					w = a + b + c + d
					if w in WORDS: results.add(w)
					if w not in PREFIXES: continue
					for e in removed(letters, w)
						w = a + b + c + d + e
						if w in WORDS: results.add(w)
						if w not in PREFIXES: continue
						for f in removed(letters, w)
							w = a + b + c + d + e + f
							if w in WORDS: results.add(w)
							if w not in PREFIXES: continue
								for g in removed(letters, w)
									w = a + b + c + d + e + g
									if w in WORDS: results.add(w)
									if not in PREFIXES: contiune
find_words