a-a a-b a-i aaa aab aaf aai aak aan aao aar ab- aba abb abf abi abk abn abo abr af- afa afb aff afi afk afn afo afr ai- aia aib aif aii aik ain aio air aka akb aki akk akn ako akr an- ana anb anf ani ank ann ano anr aoa aob aof aoi aok aon aoo aor ar- ara arb arf ari ark arn aro arr baa bab baf bai bak ban bao bar bba bbb bbf bbi bbk bbn bbo bbr bfa bfb bff bfi bfn bfo bfr bi- bia bib bif bii bik bin bio bir bka bkb bkf bkk bkn bko bkr bna bnb bnf bni bnk bnn bno bnr boa bob bof boi bok bon boo bor bra brb brf bri brk brn bro brr faa fab faf fai fak fan fao far fba fbb fbf fbi fbk fbn fbo fbr ffa fff ffi ffk ffn ffo ffr fia fib fif fii fik fin fir fka fkb fkf fki fkk fna fnb fnf fni fnk fnn fnr foa fob fof foi fok fon foo for fra frb frf fri frk frn fro frr i-f ia- iaa iab iaf iai ian iao iar iba ibb ibf ibi ibk ibn ibo ibr ifa ifb iff ifi ifn ifo ifr iia iib iif iii iin iio iir ika ikb ikf iki ikk iko ikr in- ina inb inf ini ink inn ino inr io- ioa iob iof ioi ion ioo ior ir- ira irb irf iri irk irn iro irr ka- kaa kab kaf kai kak kan kao kar kba kbb kbf kbi kbk kbn kbo kbr kfa kff kfi kfo kia kib kif kii kik kin kio kir kkb kki kkk kkn kkr kn- kna knf kni knk knn kno knr koa kob kof koi kok kon koo kor kra krf kri krk krn kro krr n-i naa nab naf nai nak nan nao nar nba nbb nbf nbi nbk nbn nbo nbr nfa nfb nff nfi nfk nfn nfo nfr nia nib nif nii nik nin nio nir nka nkf nki nkk nkn nko nkr nna nnb nnf nni nnk nnn nno no- noa nob nof noi nok non noo nor nra nrb nrf nri nrk nrn nro nrr o-i oaa oab oaf oai oak oan oao oar ob- oba obb obf obi obk obn obo obr of- ofa ofb off ofi ofn ofo ofr oia oib oif oii oik oin oio oir oka okb oki okk oko okr on- ona onb onf oni onk onn ono onr oo- ooa oob oof ooi ook oon ooo oor or- ora orb orf ori ork orn oro orr ra- raa rab raf rai rak ran rao rar rba rbb rbf rbi rbk rbn rbo rbr rfa rfb rff rfi rfk rfn rfo rfr ria rib rif rii rik rin rio rir rkb rkf rkk rko rna rnb rni rnn rno rnr roa rob rof roi rok ron roo ror rra rrb rrf rri rrk rrn rrr