ddd ddf ddi ddx ddy ddz dfd dff dfi dfx dfz di- did dif dii dix diy diz dxd dxi dxx dy- dyd dyy dzd dzi fdd fdf fdi fdx ffd fff ffi ffx ffy ffz fid fif fii fix fiz fxi fxx fy- fyi fyz fzd i-d i-f idd idf idi idx idy ifd iff ifi ifx ify ifz iid iif iii iix ixi ixy iyy izi izy izz xdf xdi xfx xii xix xxi xxx xxy xyy xyz ydy yfd yff yid yif yii yiz yxy yyf yyy yyz yzf yzy zdf zfd zfx zfy zid zif zix ziz zxx zyx zzx zzy zzz