-er eee een eep eer ees eex en- ene enn enp enr ens ep- epe epn epp epr eps epx ere ern erp err ers es- ese esn esp esr ess esx ex- exe exp exr exs exx ne- nee nen nep ner nes nex nne nnn nnp nns npe npn npp npr nps nre nrn nrp nrr nrs nrx nse nsn nsp nsr nss nsx p-p pee pen pep per pes pex pn- pne pnn pnp pnr pns pnx ppe ppn ppp ppr pps ppx pre prn prp prr prs prx ps- pse psn psp psr pss psx pxe pxr pxs re- ree ren rep rer res rex rnn rnp rnr rns rpe rpn rpp rpr rps rpx rrn rrp rrr rrs rse rsn rsp rsr rss rsx rxp rxr rxs se- see sen sep ser ses sex sne snn snp snr sns spe spn spp spr sps spx sr- sre srn srp srr srs srx ss- sse ssn ssp ssr sss ssx sxn sxs xee xen xep xer xes xex xns xpe xpn xpp xps xrx xsp xss xxp xxx