Loop of length 13 starting with a string of length 6
found after enumerating 1982 derivations:

.cc.aaaa
	rule cc -> aacab at position 0
.aacab.aaaa
	rule a ->  at position 3
.aacb.aaaa
	rule ba -> cb at position 3
.aaccb.aaa
	rule ba -> cb at position 4
.aacccb.aa
	rule ba -> cb at position 5
.aaccccb.a
	rule ba -> cb at position 6
.aacccccb.
	rule cc -> aacab at position 5
.aacccaacabb.
	rule a ->  at position 5
.aacccacabb.
	rule a ->  at position 5
.aaccccabb.
	rule cc -> aacab at position 4
.aaccaacababb.
	rule a ->  at position 7
.aaccaacbabb.
	rule ba -> cb at position 7
.aaccaaccbbb.
	rule cc -> aacab at position 6
.aaccaaaacabbbb.