-er a-a a-c aaa aac aae aag aak aao aar ac- aca acc ace acg ack aco acr aea aec aee aeg aek aeo aer ag- aga agc age agg agk ago agr aka akc ake akg akk ako akr aoa aoc aoe aog aok aoo aor ar- ara arc are arg ark aro arr c-- caa cac cae cag cak cao car cca ccc cce ccg cck cco ccr ce- cea cec cee ceg cek ceo cer cga cgc cge cgg cgo cgr cka ckc cko co- coa coc coe cog cok coo cor cra crc cre crg crk cro crr eaa eac eae eag eak eao ear ec- eca ecc ece ecg eck eco ecr eea eec eee eeg eek eeo eer ega egc ege egg ego egr eka ekc eke ekg eko ekr eo- eoa eoc eoe eog eok eoo eor era erc ere erg erk ero err gaa gac gae gag gak gao gar gca gcc gce gcg gck gco gcr ge- gea gec gee geg gek geo ger gga ggc ggg ggo ggr gka gko goa goc goe gog gok goo gor gra grc gre grg grk gro grr ka- kaa kac kae kag kak kao kar kca kcc kce kcg kck kcr ke- kea kec kee keg kek keo ker kga kgc kgo kkc kke kkk kkr koa koc koe kog kok koo kor kra krc krg krk kro krr oaa oac oae oag oak oao oar oc- oca occ ocg ock oco ocr oea oec oee oeg oeo oer oga ogc oge ogg ogo oka okc oke okg okk oko okr oo- ooa ooc oog ook ooo oor or- ora orc ore org ork oro orr ra- raa rac rae rag rak rao rar rca rcc rce rcg rco rcr re- rea rec ree reg rek reo rer rga rgc rge rgg rgk rgo rgr rkc rke rkg rkk rko roa roc roe rog rok roo ror rra rrc rrg rrk rrr