-er bbb bbd bbe bbk bbo bbr bdb bdd bde bdk bdo bdr be- beb bed bee bek beo ber bkb bke bkk bko bkr bob bod boe bok boo bor brb brd bre brk bro brr dbb dbd dbe dbk dbo dbr ddb ddd dde ddk ddo ddr de- deb ded dee dek deo der dkb dke dkk dko dkr dob dod doe dok doo dor drb drd dre drk dro drr ebb ebd ebe ebk ebo ebr ed- edb edd ede edk edo edr eeb eed eee eek eeo eer ekb ekd eke eko ekr eo- eob eod eoe eok eoo eor erb erd ere erk ero err kbb kbd kbe kbk kbo kbr kdb kde kdk kdo kdr ke- keb ked kee kek keo ker kkb kke kkk kkr kob kod koe kok koo kor krd krk kro krr ob- obb obd obe obk obo obr odb odd ode odo odr oeb oed oee oeo oer okb okd oke okk oko okr oo- oob ood ook ooo oor or- orb ord ore ork oro orr rbb rbd rbe rbk rbo rbr rdb rdd rde rdo rdr re- reb red ree rek reo rer rkb rke rkk rko rob rod roe rok roo ror rrb rrd rrk rrr