-er ddd dde ddf ddi ddr ddx de- ded dee def dei der dex dfd dfe dff dfi dfr dfx di- did die dif dii dir dix drd dre dri drr drx dxd dxi dxr dxx ed- edd ede edf edi edr edx eed eee eef eer eex ef- efd efe eff efi efr efx eid eie eif eii eir eix erd ere erf eri err ex- exd exe exi exr exx fdd fde fdf fdi fdr fdx fed fee fef fei fer fex ffd ffe fff ffi ffr ffx fid fie fif fii fir fix frd fre frf fri frr fxe fxi fxr fxx i-d i-f idd ide idf idi idr idx ie- ied iee ief iei ier iex ifd ife iff ifi ifr ifx iid iie iif iii iir iix ir- ird ire irf iri irr irx ixe ixi rdd rde rdf rdi rdr rdx re- red ree ref rei rer rex rfd rfe rff rfi rfr rid rie rif rii rir rix rrd rrf rri rrr rxr xde xdf xdi xdr xed xee xer xex xfe xfx xie xii xix xrd xrf xrx xxi xxx