-er b-u bbb bbd bbe bbk bbo bbr bbu bdb bdd bde bdk bdo bdr bdu be- beb bed bee bek beo ber beu bkb bke bkk bko bkr bob bod boe bok boo bor bou brb brd bre brk bro brr bru bub bud bue buk buo bur buu dbb dbd dbe dbk dbo dbr dbu ddb ddd dde ddk ddo ddr ddu de- deb ded dee dek deo der deu dkb dke dkk dko dkr dku dob dod doe dok doo dor dou drb drd dre drk dro drr dru dub dud due duk duo dur ebb ebd ebe ebk ebo ebr ebu ed- edb edd ede edk edo edr edu eeb eed eee eek eeo eer ekb ekd eke eko ekr eku eo- eob eod eoe eok eoo eor eou erb erd ere erk ero err eru eu- eub eud eue eur kbb kbd kbe kbk kbo kbr kbu kdb kde kdk kdo kdr kdu ke- keb ked kee kek keo ker kkb kke kkk kkr kku kob kod koe kok koo kor kou krd krk kro krr kru kub kud kue kuk kur kuu ob- obb obd obe obk obo obr obu odb odd ode odo odr odu oeb oed oee oeo oer okb okd oke okk oko okr oku oo- oob ood ook ooo oor or- orb ord ore ork oro orr oru ou- oud oue ouk ouo our rbb rbd rbe rbk rbo rbr rbu rdb rdd rde rdo rdr rdu re- reb red ree rek reo rer reu rkb rke rkk rko rku rob rod roe rok roo ror rou rrb rrd rrk rrr rru rub rud rue ruk ruo rur ruu ubb ube ubk ubo ubr ubu udb udd ude udk udo udr udu ueb ued uee uer ukb uke ukk ukr uku uob uod uoe uok uoo uor ur- urb urd ure urk uro urr uru uue uur uuu