Loop of length 6 starting with a string of length 6
found after enumerating 85 derivations:

.bba.aaa
	rule bba -> aabb at position 0
.aabb.aaa
	rule aa -> b at position 0
.bbb.aaa
	rule bba -> aabb at position 1
.baabb.aa
	rule aa -> b at position 1
.bbbb.aa
	rule bba -> aabb at position 2
.bbaabb.a
	rule bba -> aabb at position 4
.bbaaaabb.