LR

mmA = (mmb, xxx)
mmb = (xxx, mmZ)
mmZ = (mmb, xxx)
nnA = (nnb, xxx)
nnb = (nnc, nnc)
nnc = (nnZ, nnZ)
nnZ = (nnb, nnb)
ooA = (ooZ, oob)
oob = (ood, ooc)
ooc = (ooA, oox)
ood = (ooZ, ood)
ooZ = (oob, ooZ)
xxx = (xxx, xxx)