a-a a-b a-c aaa aab aac aae aak aan aas ab- aba abb abc abe abk abn abs ac- aca acb acc ace ack acn acs aea aeb aec aee aek aen aes aka akb akc ake akk akn aks an- ana anb anc ane ank ann ans as- asa asb asc ase ask asn ass baa bab bac bae bak ban bas bba bbb bbc bbe bbk bbn bbs bca bcb bcc bce bck bcn bcs be- bea beb bec bee bek ben bes bka bkb bkc bke bkk bkn bks bna bnb bnc bne bnk bnn bns bsa bsb bsc bse bsk bsn bss c-- caa cab cac cae cak can cas cba cbb cbc cbe cbk cbn cbs cca ccb ccc cce cck ccn ccs ce- cea ceb cec cee cek cen ces cka ckb ckc cks cn- cna cnb cnc cne cnn cns csa csb csc cse csk csn css eaa eab eac eae eak ean eas eba ebb ebc ebe ebk ebn ebs ec- eca ecb ecc ece eck ecn ecs eea eeb eec eee eek een ees eka ekb ekc eke eks en- ena enb enc ene enk enn ens es- esa esb esc ese esk esn ess ka- kaa kab kac kae kak kan kas kba kbb kbc kbe kbk kbn kbs kca kcb kcc kce kck kcn kcs ke- kea keb kec kee kek ken kes kkb kkc kke kkk kkn kks kn- kna knc kne knk knn ksa ksb ksc kse ksk ksn kss naa nab nac nae nak nan nas nba nbb nbc nbe nbk nbn nbs nca ncb ncc nce nck ncn ncs ne- nea neb nec nee nek nen nes nka nkc nke nkk nkn nks nna nnb nnc nne nnk nnn nns nsa nsb nsc nse nsk nsn nss saa sab sac sae sak san sas sba sbb sbc sbe sbk sbn sbs sca scb scc sce sck scn scs se- sea seb sec see sek sen ses sk- ska skb skc ske skk sks sna snb snc sne snk snn sns ss- ssa ssb ssc sse ssk ssn sss