bbb bbc bbk bbo bbs bby bcb bcc bck bco bcs bcy bkb bkc bkk bko bks bob boc bok boo bos boy bsb bsc bsk bso bss bsy by- byc byk byo bys c-- cbb cbc cbk cbo cbs cby ccb ccc cck cco ccs ckb ckc cko cks cky co- cob coc cok coo cos coy csb csc csk cso css csy cyb cyc cyk cyo cys kbb kbc kbk kbo kbs kcb kcc kck kcs kkb kkc kkk kks kky kob koc kok koo kos koy ksb ksc ksk kso kss kyc kyo kys ob- obb obc obk obo obs oby oc- ocb occ ock oco ocs okb okc okk oko oks oo- oob ooc ook ooo oos os- osb osc osk oso oss oyo oys sbb sbc sbk sbo sbs sby scb scc sck sco scs sk- skb skc skk sko sks sky sob soc sok soo sos soy ss- ssb ssc ssk sso sss sy- syb syc syk sys ybc ybs yby ycc yco ycs ycy ykk yob yoc yok yoo yos yoy ysb ysc ysk yso yss ysy yyb yyc yys yyy