a-a a-b aaa aab aao aar aas aay ab- aba abb abo abr abs aby aoa aob aoo aor aos ar- ara arb aro arr ars ary as- asa asb aso asr ass asy ay- aya ayo ayr ays baa bab bao bar bas bay bba bbb bbo bbr bbs bby boa bob boo bor bos boy bra brb bro brr brs bry bsa bsb bso bsr bss bsy by- bya byo byr bys oaa oab oao oar oas ob- oba obb obo obr obs oby oo- ooa oob ooo oor oos or- ora orb oro orr ors ory os- osa osb oso osr oss oya oyo oys ra- raa rab rao rar ras ray rba rbb rbo rbr rbs roa rob roo ror ros roy rra rrb rrr rrs rsa rsb rso rsr rss ry- rya ryo ryr rys ryy saa sab sao sar sas say sba sbb sbo sbr sbs sby soa sob soo sor sos soy sr- sra srb sro srr srs sry ss- ssa ssb sso ssr sss sy- sya syb syr sys yaa yab yao yar yas yay ybr ybs yby yob yoo yor yos yoy yra yro yrs ysa ysb yso ysr yss ysy yyb yys yyy