a-a a-b a-i aaa aab aai aak aan aao aar aas ab- aba abb abi abk abn abo abr abs ai- aia aib aii aik ain aio air ais aka akb aki akk akn ako akr aks an- ana anb ani ank ann ano anr ans aoa aob aoi aok aon aoo aor aos ar- ara arb ari ark arn aro arr ars as- asa asb asi ask asn aso asr ass baa bab bai bak ban bao bar bas bba bbb bbi bbk bbn bbo bbr bbs bi- bia bib bii bik bin bio bir bis bka bkb bkk bkn bko bkr bks bna bnb bni bnk bnn bno bnr bns boa bob boi bok bon boo bor bos bra brb bri brk brn bro brr brs bsa bsb bsi bsk bsn bso bsr bss ia- iaa iab iai ian iao iar ias iba ibb ibi ibk ibn ibo ibr ibs iia iib iii iin iio iir iis ika ikb iki ikk iko ikr iks in- ina inb ini ink inn ino inr ins io- ioa iob ioi ion ioo ior ios ir- ira irb iri irk irn iro irr irs is- isa isb isi isk isn iso isr iss ka- kaa kab kai kak kan kao kar kas kba kbb kbi kbk kbn kbo kbr kbs kia kib kii kik kin kio kir kis kkb kki kkk kkn kkr kks kn- kna kni knk knn kno knr koa kob koi kok kon koo kor kos kra kri krk krn kro krr krs ksa ksb ksi ksk ksn kso ksr kss n-i naa nab nai nak nan nao nar nas nba nbb nbi nbk nbn nbo nbr nbs nia nib nii nik nin nio nir nis nka nki nkk nkn nko nkr nks nna nnb nni nnk nnn nno nns no- noa nob noi nok non noo nor nos nra nrb nri nrk nrn nro nrr nrs nsa nsb nsi nsk nsn nso nsr nss o-i oaa oab oai oak oan oao oar oas ob- oba obb obi obk obn obo obr obs oia oib oii oik oin oio oir ois oka okb oki okk oko okr oks on- ona onb oni onk onn ono onr ons oo- ooa oob ooi ook oon ooo oor oos or- ora orb ori ork orn oro orr ors os- osa osb osi osk osn oso osr oss ra- raa rab rai rak ran rao rar ras rba rbb rbi rbk rbn rbo rbr rbs ria rib rii rik rin rio rir ris rkb rkk rko rks rna rnb rni rnn rno rnr rns roa rob roi rok ron roo ror ros rra rrb rri rrk rrn rrr rrs rsa rsb rsi rsk rsn rso rsr rss saa sab sai sak san sao sar sas sba sbb sbi sbk sbn sbo sbr sbs sia sib sii sik sin sio sir sis sk- ska skb ski skk sko skr sks sna snb sni snk snn sno snr sns soa sob soi sok son soo sor sos sr- sra srb sri srk srn sro srr srs ss- ssa ssb ssi ssk ssn sso ssr sss