bbb bbm bbo bbr bbs bbx bmb bmm bmo bmr bms bmx bob bom boo bor bos box brb brm bro brr brs brx bsb bsm bso bsr bss bsx bxb bxm bxo bxx m-o m-r mbb mbm mbo mbr mbs mbx mmb mmm mmo mmr mms mmx mob mom moo mor mos mox mrb mrm mro mrr mrs mrx msb msm mso msr mss msx mxr mxs ob- obb obm obo obr obs obx om- omb omm omo omr oms omx oo- oob oom ooo oor oos oox or- orb orm oro orr ors orx os- osb osm oso osr oss osx ox- oxb oxo oxx rbb rbm rbo rbr rbs rbx rmb rmm rmo rmr rms rmx rob rom roo ror ros rox rrb rrm rrr rrs rsb rsm rso rsr rss rsx rxr rxs sbb sbm sbo sbr sbs sbx smb smm smo smr sms smx sob som soo sor sos sox sr- srb srm sro srr srs srx ss- ssb ssm sso ssr sss ssx sxm sxs xbr xbx xmm xmo xmr xms xmx xom xoo xor xos xox xrx xsb xsm xss xxo xxx