Loop of length 26 starting with a string of length 8
found after enumerating 624 derivations:

.cbb.bbbbb
	rule cbb -> bacb at position 0
.bacb.bbbbb
	rule cbb -> bacb at position 2
.babacb.bbbb
	rule ab -> bbc at position 1
.bbbcacb.bbbb
	rule cbb -> bacb at position 5
.bbbcabacb.bbb
	rule ab -> bbc at position 4
.bbbcbbcacb.bbb
	rule cbb -> bacb at position 8
.bbbcbbcabacb.bb
	rule ab -> bbc at position 7
.bbbcbbcbbcacb.bb
	rule cbb -> bacb at position 6
.bbbcbbbacbcacb.bb
	rule cbb -> bacb at position 12
.bbbcbbbacbcabacb.b
	rule ab -> bbc at position 11
.bbbcbbbacbcbbcacb.b
	rule cbb -> bacb at position 10
.bbbcbbbacbbacbcacb.b
	rule cbb -> bacb at position 8
.bbbcbbbabacbacbcacb.b
	rule ab -> bbc at position 7
.bbbcbbbbbcacbacbcacb.b
	rule cbb -> bacb at position 18
.bbbcbbbbbcacbacbcabacb.
	rule ab -> bbc at position 17
.bbbcbbbbbcacbacbcbbcacb.
	rule cbb -> bacb at position 16
.bbbcbbbbbcacbacbbacbcacb.
	rule cbb -> bacb at position 14
.bbbcbbbbbcacbabacbacbcacb.
	rule ab -> bbc at position 13
.bbbcbbbbbcacbbbcacbacbcacb.
	rule cbb -> bacb at position 11
.bbbcbbbbbcabacbbcacbacbcacb.
	rule ab -> bbc at position 10
.bbbcbbbbbcbbcacbbcacbacbcacb.
	rule cbb -> bacb at position 9
.bbbcbbbbbbacbcacbbcacbacbcacb.
	rule cbb -> bacb at position 15
.bbbcbbbbbbacbcabacbcacbacbcacb.
	rule ab -> bbc at position 14
.bbbcbbbbbbacbcbbcacbcacbacbcacb.
	rule cbb -> bacb at position 13
.bbbcbbbbbbacbbacbcacbcacbacbcacb.
	rule cbb -> bacb at position 11
.bbbcbbbbbbabacbacbcacbcacbacbcacb.
	rule ab -> bbc at position 10
.bbbcbbbbbbbbcacbacbcacbcacbacbcacb.