Loop of length 16 starting with a string of length 6
found after enumerating 3300 derivations:

.ca.aaaa
	rule ca -> aabc at position 0
.aabc.aaaa
	rule ca -> aabc at position 3
.aabaabc.aaa
	rule baa -> ac at position 2
.aaacbc.aaa
	rule ca -> aabc at position 5
.aaacbaabc.aa
	rule baa -> ac at position 4
.aaacacbc.aa
	rule ca -> aabc at position 7
.aaacacbaabc.a
	rule baa -> ac at position 6
.aaacacacbc.a
	rule ca -> aabc at position 5
.aaacaaabccbc.a
	rule ca -> aabc at position 11
.aaacaaabccbaabc.
	rule baa -> ac at position 10
.aaacaaabccacbc.
	rule ca -> aabc at position 9
.aaacaaabcaabccbc.
	rule ca -> aabc at position 8
.aaacaaabaabcabccbc.
	rule baa -> ac at position 7
.aaacaaaacbcabccbc.
	rule ca -> aabc at position 10
.aaacaaaacbaabcbccbc.
	rule baa -> ac at position 9
.aaacaaaacacbcbccbc.
	rule ca -> aabc at position 8
.aaacaaaaaabccbcbccbc.