Loop of length 15 starting with a string of length 4
found after enumerating 490 derivations:

.cb.bb
	rule cb -> aaaac at position 0
.aaaac.bb
	rule aaa -> bc at position 0
.bcac.bb
	rule cb -> aaaac at position 3
.bcaaaaac.b
	rule aaa -> bc at position 2
.bcbcaac.b
	rule cb -> aaaac at position 6
.bcbcaaaaaac.
	rule aaa -> bc at position 4
.bcbcbcaaac.
	rule cb -> aaaac at position 3
.bcbaaaaccaaac.
	rule aaa -> bc at position 3
.bcbbcaccaaac.
	rule aaa -> bc at position 8
.bcbbcaccbcc.
	rule cb -> aaaac at position 7
.bcbbcacaaaaccc.
	rule aaa -> bc at position 7
.bcbbcacbcaccc.
	rule cb -> aaaac at position 6
.bcbbcaaaaaccaccc.
	rule aaa -> bc at position 5
.bcbbcbcaaccaccc.
	rule cb -> aaaac at position 4
.bcbbaaaaccaaccaccc.
	rule aaa -> bc at position 4
.bcbbbcaccaaccaccc.