-er b-u bbb bbe bbi bbr bbu bbx be- beb bee bei ber beu bex bez bi- bib bie bii bir biu bix biz brb bre bri brr bru brx brz bub bue bui bur buu bux buz bxb bxi bxx bze bzr bzu bzz ebb ebe ebi ebr ebu ebx eeb eee eer eex eib eie eii eir eiu eix erb ere eri err eru erz eu- eub eue eui eur eux ex- exe exi exr exu exx eze ezr ezz ibb ibe ibi ibr ibu ibx ibz ie- iee iei ier iex iib iie iii iir iiu iix ir- irb ire iri irr iru irx iu- iub iue iui iur iuz ixe ixi ize izi izu izz rbb rbe rbi rbr rbu rbx re- reb ree rei rer reu rex rez rib rie rii rir rix riz rrb rri rrr rru rub rue rui rur ruu rux ruz rxr rzb rze ubb ube ubi ubr ubu ubx ueb uee uei uer uib uie uii uir uiu ur- urb ure uri urr uru urx urz uue uur uuu uxb uxr uxu uzb uzi uzu xbe xbr xbx xee xer xeu xex xie xii xiu xix xrx xue xui xxi xxx zbb zbr zeb zee zer zez zib zie zir zix ziz zub zui zur zuz zxx zzr zzx zzz