a-a a-b a-z aaa aab aao aar aas aaz ab- aba abb abo abr abs abz aoa aob aoo aor aos ar- ara arb aro arr ars arz as- asa asb aso asr ass asz az- aza azb azo azs azz baa bab bao bar bas baz bba bbb bbo bbr bbs boa bob boo bor bos boz bra brb bro brr brs brz bsa bsb bso bsr bss bza bzo bzr bzs bzz oaa oab oao oar oas ob- oba obb obo obr obs oo- ooa oob ooo oor oos or- ora orb oro orr ors orz os- osa osb oso osr oss oza ozo ozs ozz ra- raa rab rao rar ras raz rba rbb rbo rbr rbs roa rob roo ror ros roz rra rrb rrr rrs rsa rsb rso rsr rss rza rzb rzo saa sab sao sar sas saz sba sbb sbo sbr sbs soa sob soo sor sos soz sr- sra srb sro srr srs ss- ssa ssb sso ssr sss ssz sza szr zaa zab zao zar zas zaz zbb zbr zbs zo- zoa zob zoo zor zos zro zrs zsa zsz zzr zzs zzz