bbb bbk bbo bbs bbx bby bkb bkk bko bks bkx bob bok boo bos box boy bsb bsk bso bss bsx bsy bxb bxo bxx by- byk byo bys kbb kbk kbo kbs kbx kkb kkk kks kky kob kok koo kos koy ksb ksk kso kss kxo kxy kyo kys kyx ob- obb obk obo obs obx oby okb okk oko oks oo- oob ook ooo oos oox os- osb osk oso oss osx ox- oxb oxo oxx oxy oyo oys sbb sbk sbo sbs sbx sby sk- skb skk sko sks skx sky sob sok soo sos sox soy ss- ssb ssk sso sss ssx sxs sy- syb syk sys syx xbx xkb xks xok xoo xos xox xsb xss xxo xxx xxy xyy ybs yby ykk yob yok yoo yos yox yoy ysb ysk yso yss ysy yxy yyb yys yyy