-er eee eef eep eer eet eex ef- efe eff efi efp efr eft efx eie eif eii eip eir eit eix ep- epe epf epi epp epr ept epx ere erf eri erp err ert ete etf eti etp etr ett etx ex- exe exi exp exr ext exx fee fef fei fep fer fet fex ffe fff ffi ffp ffr fft ffx fie fif fii fip fir fit fix fpe fpi fpp fpr fpt fpx fre frf fri frp frr frt fte ftf fti ftp ftr ftt ftx fxe fxi fxp fxr fxt fxx i-f ie- iee ief iei iep ier iet iex ife iff ifi ifp ifr ift ifx iie iif iii iip iir iit iix ipe ipf ipi ipp ipr ipt ipx ir- ire irf iri irp irr irt irx ite itf iti itp itt itx ixe ixi p-p pee pef pei pep per pet pex pfe pff pfi pfp pfr pft pfx pie pif pii pip pir pit pix ppe ppf ppi ppp ppr ppt ppx pre prf pri prp prr prt prx pt- pte ptf pti ptp ptr ptt ptx pxe pxr pxt re- ree ref rei rep rer ret rex rfe rff rfi rfp rfr rft rie rif rii rip rir rit rix rpe rpf rpi rpp rpr rpt rpx rrf rri rrp rrr rrt rte rtf rti rtp rtr rtt rtx rxp rxr t-x te- tee tef tei tep ter tet tex tfe tff tfi tfp tfr tft tfx tie tif tii tip tir tit tix tpe tpf tpi tpp tpr tpt tpx tre trf tri trp trr trt trx tte ttf tti ttp ttr ttt ttx txe txf txi txt xee xep xer xet xex xfe xft xfx xie xii xit xix xpe xpf xpp xpt xrf xrt xrx xtf xti xtp xtr xtx xxi xxp xxx