-er a-a a-c aaa aac aae aaf aag aak aao aar ac- aca acc ace acf acg ack aco acr aea aec aee aef aeg aek aeo aer af- afa afc afe aff afg afk afo afr ag- aga agc age agf agg agk ago agr aka akc ake akg akk ako akr aoa aoc aoe aof aog aok aoo aor ar- ara arc are arf arg ark aro arr c-- caa cac cae caf cag cak cao car cca ccc cce ccf ccg cck cco ccr ce- cea cec cee cef ceg cek ceo cer cfa cfc cfe cff cfg cfk cfo cfr cga cgc cge cgg cgo cgr cka ckc cko co- coa coc coe cof cog cok coo cor cra crc cre crf crg crk cro crr eaa eac eae eaf eag eak eao ear ec- eca ecc ece ecf ecg eck eco ecr eea eec eee eef eeg eek eeo eer ef- efa efc efe eff efg efo efr ega egc ege egf egg ego egr eka ekc eke ekf ekg eko ekr eo- eoa eoc eoe eof eog eok eoo eor era erc ere erf erg erk ero err faa fac fae faf fag fak fao far fca fcc fce fcf fcg fck fco fcr fea fec fee fef feg fek feo fer ffa ffc ffe fff ffg ffk ffo ffr fga fgc fge fgf fgg fgr fka fkc fkf fkg fkk foa foc foe fof fog fok foo for fra frc fre frf frg frk fro frr gaa gac gae gaf gag gak gao gar gca gcc gce gcf gcg gck gco gcr ge- gea gec gee gef geg gek geo ger gfa gfc gfe gff gfk gfo gfr gga ggc ggg ggo ggr gka gko goa goc goe gof gog gok goo gor gra grc gre grf grg grk gro grr ka- kaa kac kae kaf kag kak kao kar kca kcc kce kcg kck kcr ke- kea kec kee kef keg kek keo ker kfa kfc kff kfg kfo kga kgc kgf kgo kkc kke kkk kkr koa koc koe kof kog kok koo kor kra krc krf krg krk kro krr oaa oac oae oaf oag oak oao oar oc- oca occ ocf ocg ock oco ocr oea oec oee oef oeg oeo oer of- ofa ofc ofe off ofg ofo ofr oga ogc oge ogf ogg ogo oka okc oke okg okk oko okr oo- ooa ooc oof oog ook ooo oor or- ora orc ore orf org ork oro orr ra- raa rac rae raf rag rak rao rar rca rcc rce rcf rcg rco rcr re- rea rec ree ref reg rek reo rer rfa rfc rfe rff rfg rfk rfo rfr rga rgc rge rgf rgg rgk rgo rgr rkc rke rkf rkg rkk rko roa roc roe rof rog rok roo ror rra rrc rrf rrg rrk rrr