-er bbb bbc bbd bbe bbo bbr bcb bcc bcd bce bco bcr bdb bdc bdd bde bdo bdr be- beb bec bed bee beo ber bob boc bod boe boo bor brb brd bre bro brr c-- cbb cbc cbd cbe cbo cbr ccb ccc ccd cce cco ccr cdb cdc cdd cde cdo cdr ce- ceb cec ced cee ceo cer co- cob coc cod coe coo cor crb crc crd cre cro crr dbb dbc dbd dbe dbo dbr dcb dcc dcd dce dco dcr ddb ddc ddd dde ddo ddr de- deb dec ded dee deo der dob doc dod doe doo dor drb drc drd dre dro drr ebb ebc ebd ebe ebo ebr ec- ecb ecc ecd ece eco ecr ed- edb edc edd ede edo edr eeb eec eed eee eeo eer eo- eob eoc eod eoe eoo eor erb erc erd ere ero err ob- obb obc obd obe obo obr oc- ocb occ ocd oco ocr odb odc odd ode odo odr oeb oec oed oee oeo oer oo- oob ooc ood ooo oor or- orb orc ord ore oro orr rbb rbc rbd rbe rbo rbr rcb rcc rcd rce rco rcr rdb rdc rdd rde rdo rdr re- reb rec red ree reo rer rob roc rod roe roo ror rrb rrc rrd rrr