-er eee eef eer eet eex ef- efe eff efi efr eft efx eie eif eii eir eit eix ere erf eri err ert ete etf eti etr ett etx ex- exe exi exr ext exx fee fef fei fer fet fex ffe fff ffi ffr fft ffx fie fif fii fir fit fix fre frf fri frr frt fte ftf fti ftr ftt ftx fxe fxi fxr fxt fxx i-f ie- iee ief iei ier iet iex ife iff ifi ifr ift ifx iie iif iii iir iit iix ir- ire irf iri irr irt irx ite itf iti itt itx ixe ixi re- ree ref rei rer ret rex rfe rff rfi rfr rft rie rif rii rir rit rix rrf rri rrr rrt rte rtf rti rtr rtt rtx rxr t-x te- tee tef tei ter tet tex tfe tff tfi tfr tft tfx tie tif tii tir tit tix tre trf tri trr trt trx tte ttf tti ttr ttt ttx txe txf txi txt xee xer xet xex xfe xft xfx xie xii xit xix xrf xrt xrx xtf xti xtr xtx xxi xxx