-er eee eef eeo eep eer eet eex ef- efe eff efo efp efr eft efx eo- eoe eof eoo eop eor eot ep- epe epf epo epp epr ept epx ere erf ero erp err ert ete etf eto etp etr ett etx ex- exe exo exp exr ext exx fee fef feo fep fer fet fex ffe fff ffo ffp ffr fft ffx foe fof foo fop for fot fox fpe fpo fpp fpr fpt fpx fre frf fro frp frr frt fte ftf fto ftp ftr ftt ftx fxe fxp fxr fxt fxx oee oef oeo oep oer oet oex of- ofe off ofo ofp ofr oft ofx oo- oof ooo oop oor oot oox op- ope opf opo opp opr opt opx or- ore orf oro orp orr ort orx ot- ote otf oto otp otr ott ox- oxf oxo oxt oxx p-p pee pef peo pep per pet pex pfe pff pfo pfp pfr pft pfx poe pof poo pop por pot pox ppe ppf ppo ppp ppr ppt ppx pre prf pro prp prr prt prx pt- pte ptf pto ptp ptr ptt ptx pxe pxr pxt re- ree ref reo rep rer ret rex rfe rff rfo rfp rfr rft roe rof roo rop ror rot rox rpe rpf rpo rpp rpr rpt rpx rrf rrp rrr rrt rte rtf rto rtp rtr rtt rtx rxp rxr t-x te- tee tef teo tep ter tet tex tfe tff tfo tfp tfr tft tfx to- toe tof too top tor tot tox tpe tpf tpo tpp tpr tpt tpx tre trf tro trp trr trt trx tte ttf tto ttp ttr ttt ttx txe txf txt xee xep xer xet xex xfe xft xfx xof xoo xop xor xot xox xpe xpf xpo xpp xpt xrf xrt xrx xtf xtp xtr xtx xxo xxp xxx