-er a-a a-b aaa aab aae aaf aak aao aap aar ab- aba abb abe abf abk abo abp abr aea aeb aee aef aek aeo aep aer af- afa afb afe aff afk afo afp afr aka akb ake akk ako akp akr aoa aob aoe aof aok aoo aop aor ap- apa apb ape apf apk apo app apr ar- ara arb are arf ark aro arp arr b-p baa bab bae baf bak bao bap bar bba bbb bbe bbf bbk bbo bbp bbr be- bea beb bee bef bek beo bep ber bfa bfb bfe bff bfo bfp bfr bka bkb bke bkf bkk bko bkp bkr boa bob boe bof bok boo bop bor bpa bpb bpe bpf bpo bpp bpr bra brb bre brf brk bro brp brr eaa eab eae eaf eak eao eap ear eba ebb ebe ebf ebk ebo ebp ebr eea eeb eee eef eek eeo eep eer ef- efa efb efe eff efo efp efr eka ekb eke ekf eko ekp ekr eo- eoa eob eoe eof eok eoo eop eor ep- epa epb epe epf epo epp epr era erb ere erf erk ero erp err faa fab fae faf fak fao fap far fba fbb fbe fbf fbk fbo fbp fbr fea feb fee fef fek feo fep fer ffa ffe fff ffk ffo ffp ffr fka fkb fkf fkk fkp foa fob foe fof fok foo fop for fpa fpb fpe fpk fpo fpp fpr fra frb fre frf frk fro frp frr ka- kaa kab kae kaf kak kao kap kar kba kbb kbe kbf kbk kbo kbp kbr ke- kea keb kee kef kek keo kep ker kfa kff kfo kkb kke kkk kkp kkr koa kob koe kof kok koo kop kor kpa kpe kpf kpk kpo kpp kpr kra krf krk kro krp krr oaa oab oae oaf oak oao oap oar ob- oba obb obe obf obk obo obp obr oea oeb oee oef oeo oep oer of- ofa ofb ofe off ofo ofp ofr oka okb oke okk oko okp okr oo- ooa oob oof ook ooo oop oor op- opa opb ope opf opk opo opp opr or- ora orb ore orf ork oro orp orr p-p paa pab pae paf pak pao pap par pba pbb pbe pbf pbk pbo pbp pbr pea peb pee pef pek peo pep per pfa pfb pfe pff pfk pfo pfp pfr pka pkb pke pkf pko pkp pkr poa pob poe pof pok poo pop por ppa ppb ppe ppf ppk ppo ppp ppr pra prb pre prf prk pro prp prr ra- raa rab rae raf rak rao rap rar rba rbb rbe rbf rbk rbo rbp rbr re- rea reb ree ref rek reo rep rer rfa rfb rfe rff rfk rfo rfp rfr rkb rke rkf rkk rko rkp roa rob roe rof rok roo rop ror rpa rpb rpe rpf rpk rpo rpp rpr rra rrb rrf rrk rrp rrr