-er bbb bbc bbd bbe bbk bbo bbr bcb bcc bcd bce bck bco bcr bdb bdc bdd bde bdk bdo bdr be- beb bec bed bee bek beo ber bkb bkc bke bkk bko bkr bob boc bod boe bok boo bor brb brd bre brk bro brr c-- cbb cbc cbd cbe cbk cbo cbr ccb ccc ccd cce cck cco ccr cdb cdc cdd cde cdk cdo cdr ce- ceb cec ced cee cek ceo cer ckb ckc ckd cko co- cob coc cod coe cok coo cor crb crc crd cre crk cro crr dbb dbc dbd dbe dbk dbo dbr dcb dcc dcd dce dck dco dcr ddb ddc ddd dde ddk ddo ddr de- deb dec ded dee dek deo der dkb dkc dke dkk dko dkr dob doc dod doe dok doo dor drb drc drd dre drk dro drr ebb ebc ebd ebe ebk ebo ebr ec- ecb ecc ecd ece eck eco ecr ed- edb edc edd ede edk edo edr eeb eec eed eee eek eeo eer ekb ekc ekd eke eko ekr eo- eob eoc eod eoe eok eoo eor erb erc erd ere erk ero err kbb kbc kbd kbe kbk kbo kbr kcb kcc kcd kce kck kcr kdb kdc kde kdk kdo kdr ke- keb kec ked kee kek keo ker kkb kkc kke kkk kkr kob koc kod koe kok koo kor krc krd krk kro krr ob- obb obc obd obe obk obo obr oc- ocb occ ocd ock oco ocr odb odc odd ode odo odr oeb oec oed oee oeo oer okb okc okd oke okk oko okr oo- oob ooc ood ook ooo oor or- orb orc ord ore ork oro orr rbb rbc rbd rbe rbk rbo rbr rcb rcc rcd rce rco rcr rdb rdc rdd rde rdo rdr re- reb rec red ree rek reo rer rkb rkc rke rkk rko rob roc rod roe rok roo ror rrb rrc rrd rrk rrr