a-a a-b aaa aab aak aao aar aas aay ab- aba abb abk abo abr abs aby aka akb akk ako akr aks aoa aob aok aoo aor aos ar- ara arb ark aro arr ars ary as- asa asb ask aso asr ass asy ay- aya ayk ayo ayr ays baa bab bak bao bar bas bay bba bbb bbk bbo bbr bbs bby bka bkb bkk bko bkr bks boa bob bok boo bor bos boy bra brb brk bro brr brs bry bsa bsb bsk bso bsr bss bsy by- bya byk byo byr bys ka- kaa kab kak kao kar kas kay kba kbb kbk kbo kbr kbs kkb kkk kkr kks kky koa kob kok koo kor kos koy kra krk kro krr krs kry ksa ksb ksk kso ksr kss kya kyo kyr kys oaa oab oak oao oar oas ob- oba obb obk obo obr obs oby oka okb okk oko okr oks oo- ooa oob ook ooo oor oos or- ora orb ork oro orr ors ory os- osa osb osk oso osr oss oya oyo oys ra- raa rab rak rao rar ras ray rba rbb rbk rbo rbr rbs rkb rkk rko rks rky roa rob rok roo ror ros roy rra rrb rrk rrr rrs rsa rsb rsk rso rsr rss ry- rya ryk ryo ryr rys ryy saa sab sak sao sar sas say sba sbb sbk sbo sbr sbs sby sk- ska skb skk sko skr sks sky soa sob sok soo sor sos soy sr- sra srb srk sro srr srs sry ss- ssa ssb ssk sso ssr sss sy- sya syb syk syr sys yaa yab yak yao yar yas yay ybr ybs yby yka ykk yob yok yoo yor yos yoy yra yro yrs ysa ysb ysk yso ysr yss ysy yyb yys yyy