-er eee eef een eeo eer eex ef- efe eff efo efr efx en- ene enf enn eno enr eo- eoe eof eon eoo eor ere erf ern ero err ex- exe exo exr exx fee fef fen feo fer fex ffe fff ffn ffo ffr ffx fne fnf fnn fnr fnx foe fof fon foo for fox fre frf frn fro frr fxe fxr fxx ne- nee nef nen neo ner nex nfe nff nfn nfo nfr nne nnf nnn nno no- noe nof non noo nor nox nre nrf nrn nro nrr nrx oee oef oen oeo oer oex of- ofe off ofn ofo ofr ofx on- one onf onn ono onr onx oo- oof oon ooo oor oox or- ore orf orn oro orr orx ox- oxf oxn oxo oxx re- ree ref ren reo rer rex rfe rff rfn rfo rfr rnn rno rnr roe rof ron roo ror rox rrf rrn rrr rxr xee xen xer xex xfe xfn xfx xno xof xon xoo xor xox xrf xrx xxo xxx