a-a a-b aaa aab aan aao aar aas ab- aba abb abn abo abr abs an- ana anb ann ano anr ans aoa aob aon aoo aor aos ar- ara arb arn aro arr ars as- asa asb asn aso asr ass baa bab ban bao bar bas bba bbb bbn bbo bbr bbs bna bnb bnn bno bnr bns boa bob bon boo bor bos bra brb brn bro brr brs bsa bsb bsn bso bsr bss naa nab nan nao nar nas nba nbb nbn nbo nbr nbs nna nnb nnn nno nns no- noa nob non noo nor nos nra nrb nrn nro nrr nrs nsa nsb nsn nso nsr nss oaa oab oan oao oar oas ob- oba obb obn obo obr obs on- ona onb onn ono onr ons oo- ooa oob oon ooo oor oos or- ora orb orn oro orr ors os- osa osb osn oso osr oss ra- raa rab ran rao rar ras rba rbb rbn rbo rbr rbs rna rnb rnn rno rnr rns roa rob ron roo ror ros rra rrb rrn rrr rrs rsa rsb rsn rso rsr rss saa sab san sao sar sas sba sbb sbn sbo sbr sbs sna snb snn sno snr sns soa sob son soo sor sos sr- sra srb srn sro srr srs ss- ssa ssb ssn sso ssr sss