-er b-u bbb bbe bbg bbr bbu bbx be- beb bee beg ber beu bex bgb bge bgg bgr bgu bgx brb bre brg brr bru brx bub bue bug bur buu bux bxb bxx ebb ebe ebg ebr ebu ebx eeb eee eeg eer eex egb ege egg egr egu egx erb ere erg err eru eu- eub eue eug eur eux ex- exe exr exu exx gbe gbg gbr gbu gbx ge- geb gee geg ger geu gex ggb ggg ggr ggu grb gre grg grr gru grx gu- gub gue gug gur guu rbb rbe rbg rbr rbu rbx re- reb ree reg rer reu rex rgb rge rgg rgr rgx rrb rrg rrr rru rub rue rug rur ruu rux rxr ubb ube ubg ubr ubu ubx ueb uee ueg uer ugb uge ugg ugr ugu ugx ur- urb ure urg urr uru urx uue uug uur uuu uxb uxr uxu xbe xbr xbx xee xeg xer xeu xex xge xrx xue xxx