-er a-a a-c aaa aac aae aak aao aar ac- aca acc ace ack aco acr aea aec aee aek aeo aer aka akc ake akk ako akr aoa aoc aoe aok aoo aor ar- ara arc are ark aro arr c-- caa cac cae cak cao car cca ccc cce cck cco ccr ce- cea cec cee cek ceo cer cka ckc cko co- coa coc coe cok coo cor cra crc cre crk cro crr eaa eac eae eak eao ear ec- eca ecc ece eck eco ecr eea eec eee eek eeo eer eka ekc eke eko ekr eo- eoa eoc eoe eok eoo eor era erc ere erk ero err ka- kaa kac kae kak kao kar kca kcc kce kck kcr ke- kea kec kee kek keo ker kkc kke kkk kkr koa koc koe kok koo kor kra krc krk kro krr oaa oac oae oak oao oar oc- oca occ ock oco ocr oea oec oee oeo oer oka okc oke okk oko okr oo- ooa ooc ook ooo oor or- ora orc ore ork oro orr ra- raa rac rae rak rao rar rca rcc rce rco rcr re- rea rec ree rek reo rer rkc rke rkk rko roa roc roe rok roo ror rra rrc rrk rrr