bbb bbc bbm bbo bbx bcb bcc bcm bco bcx bmb bmc bmm bmo bmx bob boc bom boo box bxb bxm bxo bxx c-- cbb cbc cbm cbo cbx ccb ccc ccm cco ccx cmb cmc cmm cmo cmx co- cob coc com coo cox cxc cxo cxx m-o mbb mbc mbm mbo mbx mc- mcb mcc mcm mco mcx mmb mmc mmm mmo mmx mob moc mom moo mox mxc ob- obb obc obm obo obx oc- ocb occ ocm oco ocx om- omb omc omm omo omx oo- oob ooc oom ooo oox ox- oxb oxc oxo oxx xbc xbx xcb xcx xmc xmm xmo xmx xoc xom xoo xox xxo xxx