a-a a-b a-z aaa aab aak aao aar aas aaz ab- aba abb abk abo abr abs abz aka akb akk ako akr aks aoa aob aok aoo aor aos ar- ara arb ark aro arr ars arz as- asa asb ask aso asr ass asz az- aza azb azo azs azz baa bab bak bao bar bas baz bba bbb bbk bbo bbr bbs bka bkb bkk bko bkr bks boa bob bok boo bor bos boz bra brb brk bro brr brs brz bsa bsb bsk bso bsr bss bza bzo bzr bzs bzz k-z ka- kaa kab kak kao kar kas kaz kba kbb kbk kbo kbr kbs kbz kkb kkk kkr kks koa kob kok koo kor kos koz kra krk kro krr krs ksa ksb ksk kso ksr kss kzo oaa oab oak oao oar oas ob- oba obb obk obo obr obs oka okb okk oko okr oks oo- ooa oob ook ooo oor oos or- ora orb ork oro orr ors orz os- osa osb osk oso osr oss oza ozo ozs ozz ra- raa rab rak rao rar ras raz rba rbb rbk rbo rbr rbs rkb rkk rko rks rkz roa rob rok roo ror ros roz rra rrb rrk rrr rrs rsa rsb rsk rso rsr rss rza rzb rzo saa sab sak sao sar sas saz sba sbb sbk sbo sbr sbs sk- ska skb skk sko skr sks soa sob sok soo sor sos soz sr- sra srb srk sro srr srs ss- ssa ssb ssk sso ssr sss ssz sza szr zaa zab zak zao zar zas zaz zbb zbr zbs zka zks zo- zoa zob zok zoo zor zos zro zrs zsa zsz zzr zzs zzz