-er a-a a-c aaa aac aae aaf aak aan aao aar ac- aca acc ace acf ack acn aco acr aea aec aee aef aek aen aeo aer af- afa afc afe aff afk afn afo afr aka akc ake akk akn ako akr an- ana anc ane anf ank ann ano anr aoa aoc aoe aof aok aon aoo aor ar- ara arc are arf ark arn aro arr c-- caa cac cae caf cak can cao car cca ccc cce ccf cck ccn cco ccr ce- cea cec cee cef cek cen ceo cer cfa cfc cfe cff cfk cfn cfo cfr cka ckc cko cn- cna cnc cne cnf cnn cno cnr co- coa coc coe cof cok con coo cor cra crc cre crf crk crn cro crr eaa eac eae eaf eak ean eao ear ec- eca ecc ece ecf eck ecn eco ecr eea eec eee eef eek een eeo eer ef- efa efc efe eff efo efr eka ekc eke ekf eko ekr en- ena enc ene enf enk enn eno enr eo- eoa eoc eoe eof eok eon eoo eor era erc ere erf erk ern ero err faa fac fae faf fak fan fao far fca fcc fce fcf fck fcn fco fcr fea fec fee fef fek fen feo fer ffa ffc ffe fff ffk ffn ffo ffr fka fkc fkf fkk fna fnc fne fnf fnk fnn fnr foa foc foe fof fok fon foo for fra frc fre frf frk frn fro frr ka- kaa kac kae kaf kak kan kao kar kca kcc kce kck kcn kcr ke- kea kec kee kef kek ken keo ker kfa kfc kff kfo kkc kke kkk kkn kkr kn- kna knc kne knf knk knn kno knr koa koc koe kof kok kon koo kor kra krc krf krk krn kro krr naa nac nae naf nak nan nao nar nca ncc nce ncf nck ncn nco ncr ne- nea nec nee nef nek nen neo ner nfa nfc nfe nff nfk nfn nfo nfr nka nkc nke nkf nkk nkn nko nkr nna nnc nne nnf nnk nnn nno no- noa noc noe nof nok non noo nor nra nrc nre nrf nrk nrn nro nrr oaa oac oae oaf oak oan oao oar oc- oca occ ocf ock ocn oco ocr oea oec oee oef oen oeo oer of- ofa ofc ofe off ofn ofo ofr oka okc oke okk oko okr on- ona onc one onf onk onn ono onr oo- ooa ooc oof ook oon ooo oor or- ora orc ore orf ork orn oro orr ra- raa rac rae raf rak ran rao rar rca rcc rce rcf rcn rco rcr re- rea rec ree ref rek ren reo rer rfa rfc rfe rff rfk rfn rfo rfr rkc rke rkf rkk rko rna rnc rnn rno rnr roa roc roe rof rok ron roo ror rra rrc rrf rrk rrn rrr