a-a a-b a-i aaa aab aaf aai aak aan aao aas ab- aba abb abf abi abk abn abo abs af- afa afb aff afi afk afn afo afs ai- aia aib aif aii aik ain aio ais aka akb aki akk akn ako aks an- ana anb anf ani ank ann ano ans aoa aob aof aoi aok aon aoo aos as- asa asb asf asi ask asn aso ass baa bab baf bai bak ban bao bas bba bbb bbf bbi bbk bbn bbo bbs bfa bfb bff bfi bfn bfo bfs bi- bia bib bif bii bik bin bio bis bka bkb bkf bkk bkn bko bks bna bnb bnf bni bnk bnn bno bns boa bob bof boi bok bon boo bos bsa bsb bsf bsi bsk bsn bso bss faa fab faf fai fak fan fao fas fba fbb fbf fbi fbk fbn fbo fbs ffa fff ffi ffk ffn ffo ffs fia fib fif fii fik fin fis fka fkb fkf fki fkk fna fnb fnf fni fnk fnn fns foa fob fof foi fok fon foo fos fsa fsb fsf fsi fsk fsn fso fss i-f ia- iaa iab iaf iai ian iao ias iba ibb ibf ibi ibk ibn ibo ibs ifa ifb iff ifi ifn ifo ifs iia iib iif iii iin iio iis ika ikb ikf iki ikk iko iks in- ina inb inf ini ink inn ino ins io- ioa iob iof ioi ion ioo ios is- isa isb isf isi isk isn iso iss ka- kaa kab kaf kai kak kan kao kas kba kbb kbf kbi kbk kbn kbo kbs kfa kff kfi kfo kfs kia kib kif kii kik kin kio kis kkb kki kkk kkn kks kn- kna knf kni knk knn kno koa kob kof koi kok kon koo kos ksa ksb ksf ksi ksk ksn kso kss n-i naa nab naf nai nak nan nao nas nba nbb nbf nbi nbk nbn nbo nbs nfa nfb nff nfi nfk nfn nfo nfs nia nib nif nii nik nin nio nis nka nkf nki nkk nkn nko nks nna nnb nnf nni nnk nnn nno nns no- noa nob nof noi nok non noo nos nsa nsb nsf nsi nsk nsn nso nss o-i oaa oab oaf oai oak oan oao oas ob- oba obb obf obi obk obn obo obs of- ofa ofb off ofi ofn ofo ofs oia oib oif oii oik oin oio ois oka okb oki okk oko oks on- ona onb onf oni onk onn ono ons oo- ooa oob oof ooi ook oon ooo oos os- osa osb osf osi osk osn oso oss saa sab saf sai sak san sao sas sba sbb sbf sbi sbk sbn sbo sbs sfa sfb sff sfi sfk sfn sfo sfs sia sib sif sii sik sin sio sis sk- ska skb skf ski skk sko sks sna snb snf sni snk snn sno sns soa sob sof soi sok son soo sos ss- ssa ssb ssf ssi ssk ssn sso sss