a-a a-b aaa aab aae aak aan aas ab- aba abb abe abk abn abs aea aeb aee aek aen aes aka akb ake akk akn aks an- ana anb ane ank ann ans as- asa asb ase ask asn ass baa bab bae bak ban bas bba bbb bbe bbk bbn bbs be- bea beb bee bek ben bes bka bkb bke bkk bkn bks bna bnb bne bnk bnn bns bsa bsb bse bsk bsn bss eaa eab eae eak ean eas eba ebb ebe ebk ebn ebs eea eeb eee eek een ees eka ekb eke eks en- ena enb ene enk enn ens es- esa esb ese esk esn ess ka- kaa kab kae kak kan kas kba kbb kbe kbk kbn kbs ke- kea keb kee kek ken kes kkb kke kkk kkn kks kn- kna kne knk knn ksa ksb kse ksk ksn kss naa nab nae nak nan nas nba nbb nbe nbk nbn nbs ne- nea neb nee nek nen nes nka nke nkk nkn nks nna nnb nne nnk nnn nns nsa nsb nse nsk nsn nss saa sab sae sak san sas sba sbb sbe sbk sbn sbs se- sea seb see sek sen ses sk- ska skb ske skk sks sna snb sne snk snn sns ss- ssa ssb sse ssk ssn sss