-er bbb bbe bbg bbk bbo bbr be- beb bee beg bek beo ber bgb bge bgg bgk bgo bgr bkb bke bkg bkk bko bkr bob boe bog bok boo bor brb bre brg brk bro brr ebb ebe ebg ebk ebo ebr eeb eee eeg eek eeo eer egb ege egg ego egr ekb eke ekg eko ekr eo- eob eoe eog eok eoo eor erb ere erg erk ero err gbe gbg gbk gbo gbr ge- geb gee geg gek geo ger ggb ggg ggo ggr gkb gko gob goe gog gok goo gor grb gre grg grk gro grr kbb kbe kbk kbo kbr ke- keb kee keg kek keo ker kgb kgo kkb kke kkk kkr kob koe kog kok koo kor krg krk kro krr ob- obb obe obg obk obo obr oeb oee oeg oeo oer oge ogg ogo okb oke okg okk oko okr oo- oob oog ook ooo oor or- orb ore org ork oro orr rbb rbe rbg rbk rbo rbr re- reb ree reg rek reo rer rgb rge rgg rgk rgo rgr rkb rke rkg rkk rko rob roe rog rok roo ror rrb rrg rrk rrr