-er bbb bbe bbg bbo bbr bbx be- beb bee beg beo ber bex bgb bge bgg bgo bgr bgx bob boe bog boo bor box brb bre brg bro brr brx bxb bxo bxx ebb ebe ebg ebo ebr ebx eeb eee eeg eeo eer eex egb ege egg ego egr egx eo- eob eoe eog eoo eor erb ere erg ero err ex- exe exo exr exx gbe gbg gbo gbr gbx ge- geb gee geg geo ger gex ggb ggg ggo ggr gob goe gog goo gor gox grb gre grg gro grr grx ob- obb obe obg obo obr obx oeb oee oeg oeo oer oex oge ogg ogo ogx oo- oob oog ooo oor oox or- orb ore org oro orr orx ox- oxb oxo oxx rbb rbe rbg rbo rbr rbx re- reb ree reg reo rer rex rgb rge rgg rgo rgr rgx rob roe rog roo ror rox rrb rrg rrr rxr xbe xbr xbx xee xeg xer xex xge xog xoo xor xox xrx xxo xxx