-er a-a a-c aaa aac aae aak aao aar aas ac- aca acc ace ack aco acr acs aea aec aee aek aeo aer aes aka akc ake akk ako akr aks aoa aoc aoe aok aoo aor aos ar- ara arc are ark aro arr ars as- asa asc ase ask aso asr ass c-- caa cac cae cak cao car cas cca ccc cce cck cco ccr ccs ce- cea cec cee cek ceo cer ces cka ckc cko cks co- coa coc coe cok coo cor cos cra crc cre crk cro crr crs csa csc cse csk cso csr css eaa eac eae eak eao ear eas ec- eca ecc ece eck eco ecr ecs eea eec eee eek eeo eer ees eka ekc eke eko ekr eks eo- eoa eoc eoe eok eoo eor eos era erc ere erk ero err ers es- esa esc ese esk eso esr ess ka- kaa kac kae kak kao kar kas kca kcc kce kck kcr kcs ke- kea kec kee kek keo ker kes kkc kke kkk kkr kks koa koc koe kok koo kor kos kra krc krk kro krr krs ksa ksc kse ksk kso ksr kss oaa oac oae oak oao oar oas oc- oca occ ock oco ocr ocs oea oec oee oeo oer oes oka okc oke okk oko okr oks oo- ooa ooc ook ooo oor oos or- ora orc ore ork oro orr ors os- osa osc ose osk oso osr oss ra- raa rac rae rak rao rar ras rca rcc rce rco rcr rcs re- rea rec ree rek reo rer res rkc rke rkk rko rks roa roc roe rok roo ror ros rra rrc rrk rrr rrs rsa rsc rse rsk rso rsr rss saa sac sae sak sao sar sas sca scc sce sck sco scr scs se- sea sec see sek seo ser ses sk- ska skc ske skk sko skr sks soa soc soe sok soo sor sos sr- sra src sre srk sro srr srs ss- ssa ssc sse ssk sso ssr sss