a-a a-b a-c aaa aab aac aad aaf aak aao aar ab- aba abb abc abd abf abk abo abr ac- aca acb acc acd acf ack aco acr ad- ada adb adc add adf adk ado adr af- afa afb afc afd aff afk afo afr aka akb akc akd akk ako akr aoa aob aoc aod aof aok aoo aor ar- ara arb arc ard arf ark aro arr baa bab bac bad baf bak bao bar bba bbb bbc bbd bbf bbk bbo bbr bca bcb bcc bcd bcf bck bco bcr bda bdb bdc bdd bdf bdk bdo bdr bfa bfb bfc bfd bff bfo bfr bka bkb bkc bkf bkk bko bkr boa bob boc bod bof bok boo bor bra brb brd brf brk bro brr c-- caa cab cac cad caf cak cao car cba cbb cbc cbd cbf cbk cbo cbr cca ccb ccc ccd ccf cck cco ccr cda cdb cdc cdd cdf cdk cdo cdr cfa cfb cfc cfd cff cfk cfo cfr cka ckb ckc ckd cko co- coa cob coc cod cof cok coo cor cra crb crc crd crf crk cro crr daa dab dac dad daf dak dao dar dba dbb dbc dbd dbf dbk dbo dbr dca dcb dcc dcd dcf dck dco dcr dda ddb ddc ddd ddf ddk ddo ddr dfa dfb dfc dfd dff dfk dfo dfr dka dkb dkc dkk dko dkr doa dob doc dod dof dok doo dor dra drb drc drd drk dro drr faa fab fac fad faf fak fao far fba fbb fbc fbd fbf fbk fbo fbr fca fcb fcc fcd fcf fck fco fcr fda fdb fdc fdd fdf fdk fdo fdr ffa ffc ffd fff ffk ffo ffr fka fkb fkc fkf fkk foa fob foc fof fok foo for fra frb frc frd frf frk fro frr ka- kaa kab kac kad kaf kak kao kar kba kbb kbc kbd kbf kbk kbo kbr kca kcb kcc kcd kck kcr kda kdb kdc kdf kdk kdo kdr kfa kfc kfd kff kfo kkb kkc kkk kkr koa kob koc kod kof kok koo kor kra krc krd krf krk kro krr oaa oab oac oad oaf oak oao oar ob- oba obb obc obd obf obk obo obr oc- oca ocb occ ocd ocf ock oco ocr oda odb odc odd odf odo odr of- ofa ofb ofc ofd off ofo ofr oka okb okc okd okk oko okr oo- ooa oob ooc ood oof ook ooo oor or- ora orb orc ord orf ork oro orr ra- raa rab rac rad raf rak rao rar rba rbb rbc rbd rbf rbk rbo rbr rca rcb rcc rcd rcf rco rcr rda rdb rdc rdd rdf rdo rdr rfa rfb rfc rfd rff rfk rfo rfr rkb rkc rkf rkk rko roa rob roc rod rof rok roo ror rra rrb rrc rrd rrf rrk rrr