eee eef een eeo eep eex ef- efe eff efo efp efx en- ene enf enn eno enp eo- eoe eof eon eoo eop ep- epe epf epn epo epp epx ex- exe exo exp exx fee fef fen feo fep fex ffe fff ffn ffo ffp ffx fne fnf fnn fnp fnx foe fof fon foo fop fox fpe fpn fpo fpp fpx fxe fxp fxx ne- nee nef nen neo nep nex nfe nff nfn nfo nfp nne nnf nnn nno nnp no- noe nof non noo nop nox npe npf npn npo npp oee oef oen oeo oep oex of- ofe off ofn ofo ofp ofx on- one onf onn ono onp onx oo- oof oon ooo oop oox op- ope opf opn opo opp opx ox- oxf oxn oxo oxx p-p pee pef pen peo pep pex pfe pff pfn pfo pfp pfx pn- pne pnf pnn pno pnp pnx poe pof pon poo pop pox ppe ppf ppn ppo ppp ppx pxe xee xen xep xex xfe xfn xfx xno xof xon xoo xop xox xpe xpf xpn xpo xpp xxo xxp xxx