fff ffm ffo ffr ffs ffx fmf fmm fmo fmr fms fmx fof fom foo for fos fox frf frm fro frr frs fsf fsm fso fsr fss fsx fxm fxr fxs fxx m-f m-o m-r mff mfm mfo mfr mfs mmf mmm mmo mmr mms mmx mof mom moo mor mos mox mrf mrm mro mrr mrs mrx msf msm mso msr mss msx mxr mxs of- off ofm ofo ofr ofs ofx om- omf omm omo omr oms omx oo- oof oom ooo oor oos oox or- orf orm oro orr ors orx os- osf osm oso osr oss osx ox- oxf oxo oxx rff rfm rfo rfr rfs rmf rmm rmo rmr rms rmx rof rom roo ror ros rox rrf rrm rrr rrs rsf rsm rso rsr rss rsx rxr rxs sff sfm sfo sfr sfs sfx smf smm smo smr sms smx sof som soo sor sos sox sr- srf srm sro srr srs srx ss- ssf ssm sso ssr sss ssx sxm sxs xfm xfs xfx xmf xmm xmo xmr xms xmx xof xom xoo xor xos xox xrf xrx xsm xss xxo xxx