-er a-a a-b a-c aaa aab aac aae aak aan aao aar aas ab- aba abb abc abe abk abn abo abr abs ac- aca acb acc ace ack acn aco acr acs aea aeb aec aee aek aen aeo aer aes aka akb akc ake akk akn ako akr aks an- ana anb anc ane ank ann ano anr ans aoa aob aoc aoe aok aon aoo aor aos ar- ara arb arc are ark arn aro arr ars as- asa asb asc ase ask asn aso asr ass baa bab bac bae bak ban bao bar bas bba bbb bbc bbe bbk bbn bbo bbr bbs bca bcb bcc bce bck bcn bco bcr bcs be- bea beb bec bee bek ben beo ber bes bka bkb bkc bke bkk bkn bko bkr bks bna bnb bnc bne bnk bnn bno bnr bns boa bob boc boe bok bon boo bor bos bra brb bre brk brn bro brr brs bsa bsb bsc bse bsk bsn bso bsr bss c-- caa cab cac cae cak can cao car cas cba cbb cbc cbe cbk cbn cbo cbr cbs cca ccb ccc cce cck ccn cco ccr ccs ce- cea ceb cec cee cek cen ceo cer ces cka ckb ckc cko cks cn- cna cnb cnc cne cnn cno cnr cns co- coa cob coc coe cok con coo cor cos cra crb crc cre crk crn cro crr crs csa csb csc cse csk csn cso csr css eaa eab eac eae eak ean eao ear eas eba ebb ebc ebe ebk ebn ebo ebr ebs ec- eca ecb ecc ece eck ecn eco ecr ecs eea eeb eec eee eek een eeo eer ees eka ekb ekc eke eko ekr eks en- ena enb enc ene enk enn eno enr ens eo- eoa eob eoc eoe eok eon eoo eor eos era erb erc ere erk ern ero err ers es- esa esb esc ese esk esn eso esr ess ka- kaa kab kac kae kak kan kao kar kas kba kbb kbc kbe kbk kbn kbo kbr kbs kca kcb kcc kce kck kcn kcr kcs ke- kea keb kec kee kek ken keo ker kes kkb kkc kke kkk kkn kkr kks kn- kna knc kne knk knn kno knr koa kob koc koe kok kon koo kor kos kra krc krk krn kro krr krs ksa ksb ksc kse ksk ksn kso ksr kss naa nab nac nae nak nan nao nar nas nba nbb nbc nbe nbk nbn nbo nbr nbs nca ncb ncc nce nck ncn nco ncr ncs ne- nea neb nec nee nek nen neo ner nes nka nkc nke nkk nkn nko nkr nks nna nnb nnc nne nnk nnn nno nns no- noa nob noc noe nok non noo nor nos nra nrb nrc nre nrk nrn nro nrr nrs nsa nsb nsc nse nsk nsn nso nsr nss oaa oab oac oae oak oan oao oar oas ob- oba obb obc obe obk obn obo obr obs oc- oca ocb occ ock ocn oco ocr ocs oea oeb oec oee oen oeo oer oes oka okb okc oke okk oko okr oks on- ona onb onc one onk onn ono onr ons oo- ooa oob ooc ook oon ooo oor oos or- ora orb orc ore ork orn oro orr ors os- osa osb osc ose osk osn oso osr oss ra- raa rab rac rae rak ran rao rar ras rba rbb rbc rbe rbk rbn rbo rbr rbs rca rcb rcc rce rcn rco rcr rcs re- rea reb rec ree rek ren reo rer res rkb rkc rke rkk rko rks rna rnb rnc rnn rno rnr rns roa rob roc roe rok ron roo ror ros rra rrb rrc rrk rrn rrr rrs rsa rsb rsc rse rsk rsn rso rsr rss saa sab sac sae sak san sao sar sas sba sbb sbc sbe sbk sbn sbo sbr sbs sca scb scc sce sck scn sco scr scs se- sea seb sec see sek sen seo ser ses sk- ska skb skc ske skk sko skr sks sna snb snc sne snk snn sno snr sns soa sob soc soe sok son soo sor sos sr- sra srb src sre srk srn sro srr srs ss- ssa ssb ssc sse ssk ssn sso ssr sss