-er ddd dde ddf ddo ddr ddx de- ded dee def deo der dex dfd dfe dff dfo dfr dfx dod doe dof doo dor dox drd dre dro drr drx dxd dxo dxr dxx ed- edd ede edf edo edr edx eed eee eef eeo eer eex ef- efd efe eff efo efr efx eo- eod eoe eof eoo eor erd ere erf ero err ex- exd exe exo exr exx fdd fde fdf fdo fdr fdx fed fee fef feo fer fex ffd ffe fff ffo ffr ffx foe fof foo for fox frd fre frf fro frr fxe fxr fxx odd ode odf odo odr oed oee oef oeo oer oex of- ofd ofe off ofo ofr ofx oo- ood oof ooo oor oox or- ord ore orf oro orr orx ox- oxf oxo oxx rdd rde rdf rdo rdr rdx re- red ree ref reo rer rex rfd rfe rff rfo rfr rod roe rof roo ror rox rrd rrf rrr rxr xde xdf xdr xed xee xer xex xfe xfx xod xof xoo xor xox xrd xrf xrx xxo xxx