ddd dde ddf ddi ddx de- ded dee def dei dex dfd dfe dff dfi dfx di- did die dif dii dix dxd dxi dxx ed- edd ede edf edi edx eed eee eef eex ef- efd efe eff efi efx eid eie eif eii eix ex- exd exe exi exx fdd fde fdf fdi fdx fed fee fef fei fex ffd ffe fff ffi ffx fid fie fif fii fix fxe fxi fxx i-d i-f idd ide idf idi idx ie- ied iee ief iei iex ifd ife iff ifi ifx iid iie iif iii iix ixe ixi xde xdf xdi xed xee xex xfe xfx xie xii xix xxi xxx