bbb bbc bbd bbk bbo bbs bcb bcc bcd bck bco bcs bdb bdc bdd bdk bdo bds bkb bkc bkk bko bks bob boc bod bok boo bos bsb bsc bsd bsk bso bss c-- cbb cbc cbd cbk cbo cbs ccb ccc ccd cck cco ccs cdb cdc cdd cdk cdo cds ckb ckc ckd cko cks co- cob coc cod cok coo cos csb csc csd csk cso css dbb dbc dbd dbk dbo dbs dcb dcc dcd dck dco dcs ddb ddc ddd ddk ddo dds dkb dkc dkk dko dks dob doc dod dok doo dos dsb dsc dsd dsk dso dss kbb kbc kbd kbk kbo kbs kcb kcc kcd kck kcs kdb kdc kdk kdo kds kkb kkc kkk kks kob koc kod kok koo kos ksb ksc ksd ksk kso kss ob- obb obc obd obk obo obs oc- ocb occ ocd ock oco ocs odb odc odd odo ods okb okc okd okk oko oks oo- oob ooc ood ook ooo oos os- osb osc osd osk oso oss sbb sbc sbd sbk sbo sbs scb scc scd sck sco scs sdb sdc sdd sdk sdo sds sk- skb skc skd skk sko sks sob soc sod sok soo sos ss- ssb ssc ssd ssk sso sss