a-a a-b a-c aaa aab aac aak aan aar aas ab- aba abb abc abk abn abr abs ac- aca acb acc ack acn acr acs aka akb akc akk akn akr aks an- ana anb anc ank ann anr ans ar- ara arb arc ark arn arr ars as- asa asb asc ask asn asr ass baa bab bac bak ban bar bas bba bbb bbc bbk bbn bbr bbs bca bcb bcc bck bcn bcr bcs bka bkb bkc bkk bkn bkr bks bna bnb bnc bnk bnn bnr bns bra brb brk brn brr brs bsa bsb bsc bsk bsn bsr bss c-- caa cab cac cak can car cas cba cbb cbc cbk cbn cbr cbs cca ccb ccc cck ccn ccr ccs cka ckb ckc cks cn- cna cnb cnc cnn cnr cns cra crb crc crk crn crr crs csa csb csc csk csn csr css ka- kaa kab kac kak kan kar kas kba kbb kbc kbk kbn kbr kbs kca kcb kcc kck kcn kcr kcs kkb kkc kkk kkn kkr kks kn- kna knc knk knn knr kra krc krk krn krr krs ksa ksb ksc ksk ksn ksr kss naa nab nac nak nan nar nas nba nbb nbc nbk nbn nbr nbs nca ncb ncc nck ncn ncr ncs nka nkc nkk nkn nkr nks nna nnb nnc nnk nnn nns nra nrb nrc nrk nrn nrr nrs nsa nsb nsc nsk nsn nsr nss ra- raa rab rac rak ran rar ras rba rbb rbc rbk rbn rbr rbs rca rcb rcc rcn rcr rcs rkb rkc rkk rks rna rnb rnc rnn rnr rns rra rrb rrc rrk rrn rrr rrs rsa rsb rsc rsk rsn rsr rss saa sab sac sak san sar sas sba sbb sbc sbk sbn sbr sbs sca scb scc sck scn scr scs sk- ska skb skc skk skr sks sna snb snc snk snn snr sns sr- sra srb src srk srn srr srs ss- ssa ssb ssc ssk ssn ssr sss