a-a a-b a-i aaa aab aai aan aao aar aas ab- aba abb abi abn abo abr abs ai- aia aib aii ain aio air ais an- ana anb ani ann ano anr ans aoa aob aoi aon aoo aor aos ar- ara arb ari arn aro arr ars as- asa asb asi asn aso asr ass baa bab bai ban bao bar bas bba bbb bbi bbn bbo bbr bbs bi- bia bib bii bin bio bir bis bna bnb bni bnn bno bnr bns boa bob boi bon boo bor bos bra brb bri brn bro brr brs bsa bsb bsi bsn bso bsr bss ia- iaa iab iai ian iao iar ias iba ibb ibi ibn ibo ibr ibs iia iib iii iin iio iir iis in- ina inb ini inn ino inr ins io- ioa iob ioi ion ioo ior ios ir- ira irb iri irn iro irr irs is- isa isb isi isn iso isr iss n-i naa nab nai nan nao nar nas nba nbb nbi nbn nbo nbr nbs nia nib nii nin nio nir nis nna nnb nni nnn nno nns no- noa nob noi non noo nor nos nra nrb nri nrn nro nrr nrs nsa nsb nsi nsn nso nsr nss o-i oaa oab oai oan oao oar oas ob- oba obb obi obn obo obr obs oia oib oii oin oio oir ois on- ona onb oni onn ono onr ons oo- ooa oob ooi oon ooo oor oos or- ora orb ori orn oro orr ors os- osa osb osi osn oso osr oss ra- raa rab rai ran rao rar ras rba rbb rbi rbn rbo rbr rbs ria rib rii rin rio rir ris rna rnb rni rnn rno rnr rns roa rob roi ron roo ror ros rra rrb rri rrn rrr rrs rsa rsb rsi rsn rso rsr rss saa sab sai san sao sar sas sba sbb sbi sbn sbo sbr sbs sia sib sii sin sio sir sis sna snb sni snn sno snr sns soa sob soi son soo sor sos sr- sra srb sri srn sro srr srs ss- ssa ssb ssi ssn sso ssr sss