-er b-u bbb bbe bbi bbr bbu bbx be- beb bee bei ber beu bex bi- bib bie bii bir biu bix brb bre bri brr bru brx bub bue bui bur buu bux bxb bxi bxx ebb ebe ebi ebr ebu ebx eeb eee eer eex eib eie eii eir eiu eix erb ere eri err eru eu- eub eue eui eur eux ex- exe exi exr exu exx ibb ibe ibi ibr ibu ibx ie- iee iei ier iex iib iie iii iir iiu iix ir- irb ire iri irr iru irx iu- iub iue iui iur ixe ixi rbb rbe rbi rbr rbu rbx re- reb ree rei rer reu rex rib rie rii rir rix rrb rri rrr rru rub rue rui rur ruu rux rxr ubb ube ubi ubr ubu ubx ueb uee uei uer uib uie uii uir uiu ur- urb ure uri urr uru urx uue uur uuu uxb uxr uxu xbe xbr xbx xee xer xeu xex xie xii xiu xix xrx xue xui xxi xxx