bbb bbk bbo bbr bbs bby bkb bkk bko bkr bks bob bok boo bor bos boy brb brk bro brr brs bry bsb bsk bso bsr bss bsy by- byk byo byr bys kbb kbk kbo kbr kbs kkb kkk kkr kks kky kob kok koo kor kos koy krk kro krr krs kry ksb ksk kso ksr kss kyo kyr kys ob- obb obk obo obr obs oby okb okk oko okr oks oo- oob ook ooo oor oos or- orb ork oro orr ors ory os- osb osk oso osr oss oyo oys rbb rbk rbo rbr rbs rkb rkk rko rks rky rob rok roo ror ros roy rrb rrk rrr rrs rsb rsk rso rsr rss ry- ryk ryo ryr rys ryy sbb sbk sbo sbr sbs sby sk- skb skk sko skr sks sky sob sok soo sor sos soy sr- srb srk sro srr srs sry ss- ssb ssk sso ssr sss sy- syb syk syr sys ybr ybs yby ykk yob yok yoo yor yos yoy yro yrs ysb ysk yso ysr yss ysy yyb yys yyy