-er eee eep eer eet eex eie eii eip eir eit eix ep- epe epi epp epr ept epx ere eri erp err ert ete eti etp etr ett etx ex- exe exi exp exr ext exx ie- iee iei iep ier iet iex iie iii iip iir iit iix ipe ipi ipp ipr ipt ipx ir- ire iri irp irr irt irx ite iti itp itt itx ixe ixi p-p pee pei pep per pet pex pie pii pip pir pit pix ppe ppi ppp ppr ppt ppx pre pri prp prr prt prx pt- pte pti ptp ptr ptt ptx pxe pxr pxt re- ree rei rep rer ret rex rie rii rip rir rit rix rpe rpi rpp rpr rpt rpx rri rrp rrr rrt rte rti rtp rtr rtt rtx rxp rxr t-x te- tee tei tep ter tet tex tie tii tip tir tit tix tpe tpi tpp tpr tpt tpx tre tri trp trr trt trx tte tti ttp ttr ttt ttx txe txi txt xee xep xer xet xex xie xii xit xix xpe xpp xpt xrt xrx xti xtp xtr xtx xxi xxp xxx