a-a a-b aaa aab aak aan aas ab- aba abb abk abn abs aka akb akk akn aks an- ana anb ank ann ans as- asa asb ask asn ass baa bab bak ban bas bba bbb bbk bbn bbs bka bkb bkk bkn bks bna bnb bnk bnn bns bsa bsb bsk bsn bss ka- kaa kab kak kan kas kba kbb kbk kbn kbs kkb kkk kkn kks kn- kna knk knn ksa ksb ksk ksn kss naa nab nak nan nas nba nbb nbk nbn nbs nka nkk nkn nks nna nnb nnk nnn nns nsa nsb nsk nsn nss saa sab sak san sas sba sbb sbk sbn sbs sk- ska skb skk sks sna snb snk snn sns ss- ssa ssb ssk ssn sss