Loop of length 4 starting with a string of length 8
found after enumerating 6 derivations:

.abcb.cbcb
	rule abcb -> bcbcaab at position 0
.bcbcaab.cbcb
	rule abcb -> bcbcaab at position 5
.bcbcabcbcaab.cb
	rule abcb -> bcbcaab at position 10
.bcbcabcbcabcbcaab.
	rule abcb -> bcbcaab at position 9
.bcbcabcbcbcbcaabcaab.