-er eee eef een eep eer eex ef- efe eff efi efp efr efx eie eif eii ein eip eir eix en- ene enf eni enn enp enr ep- epe epf epi epn epp epr epx ere erf eri ern erp err ex- exe exi exp exr exx fee fef fei fen fep fer fex ffe fff ffi ffn ffp ffr ffx fie fif fii fin fip fir fix fne fnf fni fnn fnp fnr fnx fpe fpi fpn fpp fpr fpx fre frf fri frn frp frr fxe fxi fxp fxr fxx i-f ie- iee ief iei ien iep ier iex ife iff ifi ifn ifp ifr ifx iie iif iii iin iip iir iix in- ine inf ini inn inp inr inx ipe ipf ipi ipn ipp ipr ipx ir- ire irf iri irn irp irr irx ixe ixi ixn n-i ne- nee nef nei nen nep ner nex nfe nff nfi nfn nfp nfr nie nif nii nin nip nir nix nne nnf nni nnn nnp npe npf npi npn npp npr nre nrf nri nrn nrp nrr nrx p-p pee pef pei pen pep per pex pfe pff pfi pfn pfp pfr pfx pie pif pii pin pip pir pix pn- pne pnf pni pnn pnp pnr pnx ppe ppf ppi ppn ppp ppr ppx pre prf pri prn prp prr prx pxe pxr re- ree ref rei ren rep rer rex rfe rff rfi rfn rfp rfr rie rif rii rin rip rir rix rni rnn rnp rnr rpe rpf rpi rpn rpp rpr rpx rrf rri rrn rrp rrr rxp rxr xee xen xep xer xex xfe xfn xfx xie xii xin xix xpe xpf xpn xpp xrf xrx xxi xxp xxx