a-a a-b aaa aab aae aaf aak aan aas ab- aba abb abe abf abk abn abs aea aeb aee aef aek aen aes af- afa afb afe aff afk afn afs aka akb ake akk akn aks an- ana anb ane anf ank ann ans as- asa asb ase asf ask asn ass baa bab bae baf bak ban bas bba bbb bbe bbf bbk bbn bbs be- bea beb bee bef bek ben bes bfa bfb bfe bff bfn bfs bka bkb bke bkf bkk bkn bks bna bnb bne bnf bnk bnn bns bsa bsb bse bsf bsk bsn bss eaa eab eae eaf eak ean eas eba ebb ebe ebf ebk ebn ebs eea eeb eee eef eek een ees ef- efa efb efe eff efs eka ekb eke ekf eks en- ena enb ene enf enk enn ens es- esa esb ese esf esk esn ess faa fab fae faf fak fan fas fba fbb fbe fbf fbk fbn fbs fea feb fee fef fek fen fes ffa ffe fff ffk ffn ffs fka fkb fkf fkk fna fnb fne fnf fnk fnn fns fsa fsb fse fsf fsk fsn fss ka- kaa kab kae kaf kak kan kas kba kbb kbe kbf kbk kbn kbs ke- kea keb kee kef kek ken kes kfa kff kfs kkb kke kkk kkn kks kn- kna kne knf knk knn ksa ksb kse ksf ksk ksn kss naa nab nae naf nak nan nas nba nbb nbe nbf nbk nbn nbs ne- nea neb nee nef nek nen nes nfa nfb nfe nff nfk nfn nfs nka nke nkf nkk nkn nks nna nnb nne nnf nnk nnn nns nsa nsb nse nsf nsk nsn nss saa sab sae saf sak san sas sba sbb sbe sbf sbk sbn sbs se- sea seb see sef sek sen ses sfa sfb sfe sff sfk sfn sfs sk- ska skb ske skf skk sks sna snb sne snf snk snn sns ss- ssa ssb sse ssf ssk ssn sss