a-a a-b aaa aab aaf aan aao aar aas ab- aba abb abf abn abo abr abs af- afa afb aff afn afo afr afs an- ana anb anf ann ano anr ans aoa aob aof aon aoo aor aos ar- ara arb arf arn aro arr ars as- asa asb asf asn aso asr ass baa bab baf ban bao bar bas bba bbb bbf bbn bbo bbr bbs bfa bfb bff bfn bfo bfr bfs bna bnb bnf bnn bno bnr bns boa bob bof bon boo bor bos bra brb brf brn bro brr brs bsa bsb bsf bsn bso bsr bss faa fab faf fan fao far fas fba fbb fbf fbn fbo fbr fbs ffa fff ffn ffo ffr ffs fna fnb fnf fnn fnr fns foa fob fof fon foo for fos fra frb frf frn fro frr frs fsa fsb fsf fsn fso fsr fss naa nab naf nan nao nar nas nba nbb nbf nbn nbo nbr nbs nfa nfb nff nfn nfo nfr nfs nna nnb nnf nnn nno nns no- noa nob nof non noo nor nos nra nrb nrf nrn nro nrr nrs nsa nsb nsf nsn nso nsr nss oaa oab oaf oan oao oar oas ob- oba obb obf obn obo obr obs of- ofa ofb off ofn ofo ofr ofs on- ona onb onf onn ono onr ons oo- ooa oob oof oon ooo oor oos or- ora orb orf orn oro orr ors os- osa osb osf osn oso osr oss ra- raa rab raf ran rao rar ras rba rbb rbf rbn rbo rbr rbs rfa rfb rff rfn rfo rfr rfs rna rnb rnn rno rnr rns roa rob rof ron roo ror ros rra rrb rrf rrn rrr rrs rsa rsb rsf rsn rso rsr rss saa sab saf san sao sar sas sba sbb sbf sbn sbo sbr sbs sfa sfb sff sfn sfo sfr sfs sna snb snf snn sno snr sns soa sob sof son soo sor sos sr- sra srb srf srn sro srr srs ss- ssa ssb ssf ssn sso ssr sss