-er b-u bbb bbe bbn bbr bbu bbx be- beb bee ben ber beu bex bnb bne bnn bnr bnu bnx brb bre brn brr bru brx bub bue bun bur buu bux bxb bxn bxx ebb ebe ebn ebr ebu ebx eeb eee een eer eex en- enb ene enn enr enu erb ere ern err eru eu- eub eue eun eur eux ex- exe exr exu exx nbb nbe nbn nbr nbu nbx ne- neb nee nen ner neu nex nnb nne nnn nnu nrb nre nrn nrr nru nrx nub nue nun nur nuu nux rbb rbe rbn rbr rbu rbx re- reb ree ren rer reu rex rnb rnn rnr rnu rrb rrn rrr rru rub rue run rur ruu rux rxr ubb ube ubn ubr ubu ubx ueb uee uen uer un- unb une unn unr unu unx ur- urb ure urn urr uru urx uue uun uur uuu uxb uxr uxu xbe xbr xbx xee xen xer xeu xex xnu xrx xue xun xxx