a-a a-b aaa aab aaf aak aan aao aap aar ab- aba abb abf abk abn abo abp abr af- afa afb aff afk afn afo afp afr aka akb akk akn ako akp akr an- ana anb anf ank ann ano anp anr aoa aob aof aok aon aoo aop aor ap- apa apb apf apk apn apo app apr ar- ara arb arf ark arn aro arp arr b-p baa bab baf bak ban bao bap bar bba bbb bbf bbk bbn bbo bbp bbr bfa bfb bff bfn bfo bfp bfr bka bkb bkf bkk bkn bko bkp bkr bna bnb bnf bnk bnn bno bnp bnr boa bob bof bok bon boo bop bor bpa bpb bpf bpn bpo bpp bpr bra brb brf brk brn bro brp brr faa fab faf fak fan fao fap far fba fbb fbf fbk fbn fbo fbp fbr ffa fff ffk ffn ffo ffp ffr fka fkb fkf fkk fkp fna fnb fnf fnk fnn fnp fnr foa fob fof fok fon foo fop for fpa fpb fpk fpn fpo fpp fpr fra frb frf frk frn fro frp frr ka- kaa kab kaf kak kan kao kap kar kba kbb kbf kbk kbn kbo kbp kbr kfa kff kfo kkb kkk kkn kkp kkr kn- kna knf knk knn kno knp knr koa kob kof kok kon koo kop kor kpa kpf kpk kpn kpo kpp kpr kra krf krk krn kro krp krr naa nab naf nak nan nao nap nar nba nbb nbf nbk nbn nbo nbp nbr nfa nfb nff nfk nfn nfo nfp nfr nka nkf nkk nkn nko nkp nkr nna nnb nnf nnk nnn nno nnp no- noa nob nof nok non noo nop nor npa npb npf npn npo npp npr nra nrb nrf nrk nrn nro nrp nrr oaa oab oaf oak oan oao oap oar ob- oba obb obf obk obn obo obp obr of- ofa ofb off ofn ofo ofp ofr oka okb okk oko okp okr on- ona onb onf onk onn ono onp onr oo- ooa oob oof ook oon ooo oop oor op- opa opb opf opk opn opo opp opr or- ora orb orf ork orn oro orp orr p-p paa pab paf pak pan pao pap par pba pbb pbf pbk pbn pbo pbp pbr pfa pfb pff pfk pfn pfo pfp pfr pka pkb pkf pkn pko pkp pkr pn- pna pnb pnf pnk pnn pno pnp pnr poa pob pof pok pon poo pop por ppa ppb ppf ppk ppn ppo ppp ppr pra prb prf prk prn pro prp prr ra- raa rab raf rak ran rao rap rar rba rbb rbf rbk rbn rbo rbp rbr rfa rfb rff rfk rfn rfo rfp rfr rkb rkf rkk rko rkp rna rnb rnn rno rnp rnr roa rob rof rok ron roo rop ror rpa rpb rpf rpk rpn rpo rpp rpr rra rrb rrf rrk rrn rrp rrr