bbb bbc bbf bbo bbs bcb bcc bcf bco bcs bfb bfc bff bfo bfs bob boc bof boo bos bsb bsc bsf bso bss c-- cbb cbc cbf cbo cbs ccb ccc ccf cco ccs cfb cfc cff cfo cfs co- cob coc cof coo cos csb csc csf cso css fbb fbc fbf fbo fbs fcb fcc fcf fco fcs ffc fff ffo ffs fob foc fof foo fos fsb fsc fsf fso fss ob- obb obc obf obo obs oc- ocb occ ocf oco ocs of- ofb ofc off ofo ofs oo- oob ooc oof ooo oos os- osb osc osf oso oss sbb sbc sbf sbo sbs scb scc scf sco scs sfb sfc sff sfo sfs sob soc sof soo sos ss- ssb ssc ssf sso sss