def subSeqRec(str_, n, index = -1, curr = "", diff=0, dict_={}, j=0):
	if j==1:
		return
	if index == n:
		j+=1
		return dict_
 
	if diff not in dict_:
		dict_[diff] = []
 
	dict_[diff] += [curr]
 
	for i in range(index+1, n):
		curr += str_[i]
		subSeqRec(str_, n, i, curr, i-j, dict_, j)
 
		curr = curr[:-1]
	return dict_
 
def subSeq(str_):
	return subSeqRec(str_, len(str_), curr = str_[0])
 
str_ = input()
max_dict = subSeq(str_)
print(max_dict)

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

YWFhYmI=

aaabb