Loop of length 14 starting with a string of length 6
found after enumerating 4189 derivations:

.ca.aaaa
	rule ca -> aabc at position 0
.aabc.aaaa
	rule ca -> aabc at position 3
.aabaabc.aaa
	rule a ->  at position 3
.aababc.aaa
	rule a ->  at position 3
.aabbc.aaa
	rule bb -> c at position 2
.aacc.aaa
	rule ca -> aabc at position 3
.aacaabc.aa
	rule ca -> aabc at position 6
.aacaabaabc.a
	rule a ->  at position 6
.aacaababc.a
	rule a ->  at position 6
.aacaabbc.a
	rule bb -> c at position 5
.aacaacc.a
	rule ca -> aabc at position 6
.aacaacaabc.
	rule ca -> aabc at position 5
.aacaaaabcabc.
	rule ab ->  at position 6
.aacaaacabc.
	rule ca -> aabc at position 6
.aacaaaaabcbc.