Loop of length 13 starting with a string of length 15
found after enumerating 33002 derivations:

.aabb.abbbbbbabbb
	rule aabb -> bbbaaa at position 0
.bbbaaa.abbbbbbabbb
	rule aabb -> bbbaaa at position 5
.bbbaabbbaaa.bbbbabbb
	rule aabb -> bbbaaa at position 3
.bbbbbbaaabaaa.bbbbabbb
	rule a ->  at position 10
.bbbbbbaaabaa.bbbbabbb
	rule aabb -> bbbaaa at position 10
.bbbbbbaaabbbbaaa.bbabbb
	rule aabb -> bbbaaa at position 7
.bbbbbbabbbaaabbaaa.bbabbb
	rule aabb -> bbbaaa at position 16
.bbbbbbabbbaaabbabbbaaa.abbb
	rule aabb -> bbbaaa at position 21
.bbbbbbabbbaaabbabbbaabbbaaa.b
	rule aabb -> bbbaaa at position 19
.bbbbbbabbbaaabbabbbbbbaaabaaa.b
	rule a ->  at position 26
.bbbbbbabbbaaabbabbbbbbaaabaa.b
	rule a ->  at position 26
.bbbbbbabbbaaabbabbbbbbaaaba.b
	rule a ->  at position 26
.bbbbbbabbbaaabbabbbbbbaaab.b
	rule aabb -> bbbaaa at position 23
.bbbbbbabbbaaabbabbbbbbabbbaaa.