-er eee eef een eeo eep eer eex ef- efe eff efo efp efr efx en- ene enf enn eno enp enr eo- eoe eof eon eoo eop eor ep- epe epf epn epo epp epr epx ere erf ern ero erp err ex- exe exo exp exr exx fee fef fen feo fep fer fex ffe fff ffn ffo ffp ffr ffx fne fnf fnn fnp fnr fnx foe fof fon foo fop for fox fpe fpn fpo fpp fpr fpx fre frf frn fro frp frr fxe fxp fxr fxx ne- nee nef nen neo nep ner nex nfe nff nfn nfo nfp nfr nne nnf nnn nno nnp no- noe nof non noo nop nor nox npe npf npn npo npp npr nre nrf nrn nro nrp nrr nrx oee oef oen oeo oep oer oex of- ofe off ofn ofo ofp ofr ofx on- one onf onn ono onp onr onx oo- oof oon ooo oop oor oox op- ope opf opn opo opp opr opx or- ore orf orn oro orp orr orx ox- oxf oxn oxo oxx p-p pee pef pen peo pep per pex pfe pff pfn pfo pfp pfr pfx pn- pne pnf pnn pno pnp pnr pnx poe pof pon poo pop por pox ppe ppf ppn ppo ppp ppr ppx pre prf prn pro prp prr prx pxe pxr re- ree ref ren reo rep rer rex rfe rff rfn rfo rfp rfr rnn rno rnp rnr roe rof ron roo rop ror rox rpe rpf rpn rpo rpp rpr rpx rrf rrn rrp rrr rxp rxr xee xen xep xer xex xfe xfn xfx xno xof xon xoo xop xor xox xpe xpf xpn xpo xpp xrf xrx xxo xxp xxx