bbb bbk bbn bbo bbs bkb bkk bkn bko bks bnb bnk bnn bno bns bob bok bon boo bos bsb bsk bsn bso bss kbb kbk kbn kbo kbs kkb kkk kkn kks kn- knk knn kno kob kok kon koo kos ksb ksk ksn kso kss nbb nbk nbn nbo nbs nkk nkn nko nks nnb nnk nnn nno nns no- nob nok non noo nos nsb nsk nsn nso nss ob- obb obk obn obo obs okb okk oko oks on- onb onk onn ono ons oo- oob ook oon ooo oos os- osb osk osn oso oss sbb sbk sbn sbo sbs sk- skb skk sko sks snb snk snn sno sns sob sok son soo sos ss- ssb ssk ssn sso sss