-er a-a a-c aaa aac aae aag aao aar ac- aca acc ace acg aco acr aea aec aee aeg aeo aer ag- aga agc age agg ago agr aoa aoc aoe aog aoo aor ar- ara arc are arg aro arr c-- caa cac cae cag cao car cca ccc cce ccg cco ccr ce- cea cec cee ceg ceo cer cga cgc cge cgg cgo cgr co- coa coc coe cog coo cor cra crc cre crg cro crr eaa eac eae eag eao ear ec- eca ecc ece ecg eco ecr eea eec eee eeg eeo eer ega egc ege egg ego egr eo- eoa eoc eoe eog eoo eor era erc ere erg ero err gaa gac gae gag gao gar gca gcc gce gcg gco gcr ge- gea gec gee geg geo ger gga ggc ggg ggo ggr goa goc goe gog goo gor gra grc gre grg gro grr oaa oac oae oag oao oar oc- oca occ ocg oco ocr oea oec oee oeg oeo oer oga ogc oge ogg ogo oo- ooa ooc oog ooo oor or- ora orc ore org oro orr ra- raa rac rae rag rao rar rca rcc rce rcg rco rcr re- rea rec ree reg reo rer rga rgc rge rgg rgo rgr roa roc roe rog roo ror rra rrc rrg rrr