-er eee eef eer ees eet eex ef- efe eff efi efr efs eft efx eie eif eii eir eis eit eix ere erf eri err ers ert es- ese esf esi esr ess est esx ete etf eti etr ets ett etx ex- exe exi exr exs ext exx fee fef fei fer fes fet fex ffe fff ffi ffr ffs fft ffx fie fif fii fir fis fit fix fre frf fri frr frs frt fse fsf fsi fsr fss fst fsx fte ftf fti ftr fts ftt ftx fxe fxi fxr fxs fxt fxx i-f ie- iee ief iei ier ies iet iex ife iff ifi ifr ifs ift ifx iie iif iii iir iis iit iix ir- ire irf iri irr irs irt irx is- ise isf isi isr iss ist ite itf iti its itt itx ixe ixi re- ree ref rei rer res ret rex rfe rff rfi rfr rfs rft rie rif rii rir ris rit rix rrf rri rrr rrs rrt rse rsf rsi rsr rss rst rsx rte rtf rti rtr rts rtt rtx rxr rxs se- see sef sei ser ses set sex sfe sff sfi sfr sfs sft sfx sie sif sii sir sis sit six sr- sre srf sri srr srs srt srx ss- sse ssf ssi ssr sss sst ssx ste stf sti str sts stt stx sxi sxs sxt t-x te- tee tef tei ter tes tet tex tfe tff tfi tfr tfs tft tfx tie tif tii tir tis tit tix tre trf tri trr trs trt trx tse tsf tsi tsr tss tst tsx tte ttf tti ttr tts ttt ttx txe txf txi txs txt xee xer xes xet xex xfe xfs xft xfx xie xii xis xit xix xrf xrt xrx xsi xss xst xtf xti xtr xts xtx xxi xxx