-er b-u bbb bbe bbr bbt bbu be- beb bee ber bet beu bez brb bre brr brt bru brz btb bte btr btt btu btz bub bue bur but buu buz bze bzr bzu bzz ebb ebe ebr ebt ebu eeb eee eer eet erb ere err ert eru erz etb ete etr ett etu etz eu- eub eue eur eut eze ezr ezz rbb rbe rbr rbt rbu re- reb ree rer ret reu rez rrb rrr rrt rru rtb rte rtr rtt rtu rtz rub rue rur rut ruu ruz rzb rze tbb tbe tbr tbt tbu tbz te- teb tee ter tet teu tez trb tre trr trt tru trz ttb tte ttr ttt ttu tub tue tur tut tuu tuz tze tzu ubb ube ubr ubt ubu ueb uee uer uet ur- urb ure urr urt uru urz utb ute utr utt utu utz uue uur uut uuu uzb uzu zbb zbr zbt zeb zee zer zet zez zte ztr zub zur zut zuz zzr zzt zzz