Loop of length 14 starting with a string of length 6
found after enumerating 2021 derivations:

.ca.aaaa
	rule ca -> aaabc at position 0
.aaabc.aaaa
	rule ca -> aaabc at position 4
.aaabaaabc.aaa
	rule a ->  at position 4
.aaabaabc.aaa
	rule a ->  at position 4
.aaababc.aaa
	rule a ->  at position 4
.aaabbc.aaa
	rule ca -> aaabc at position 5
.aaabbaaabc.aa
	rule bba -> c at position 3
.aaacaabc.aa
	rule ca -> aaabc at position 7
.aaacaabaaabc.a
	rule a ->  at position 7
.aaacaabaabc.a
	rule a ->  at position 7
.aaacaababc.a
	rule a ->  at position 7
.aaacaabbc.a
	rule ca -> aaabc at position 8
.aaacaabbaaabc.
	rule bba -> c at position 6
.aaacaacaabc.
	rule ca -> aaabc at position 6
.aaacaaaaabcabc.