-er bbb bbc bbe bbk bbm bbo bbr bcb bcc bce bck bcm bco bcr be- beb bec bee bek bem beo ber bkb bkc bke bkk bkm bko bkr bmb bmc bme bmk bmm bmo bmr bob boc boe bok bom boo bor brb bre brk brm bro brr c-- cbb cbc cbe cbk cbm cbo cbr ccb ccc cce cck ccm cco ccr ce- ceb cec cee cek cem ceo cer ckb ckc ckm cko cmb cmc cme cmk cmm cmo cmr co- cob coc coe cok com coo cor crb crc cre crk crm cro crr ebb ebc ebe ebk ebm ebo ebr ec- ecb ecc ece eck ecm eco ecr eeb eec eee eek eem eeo eer ekb ekc eke eko ekr em- emb emc eme emk emm emo emr eo- eob eoc eoe eok eom eoo eor erb erc ere erk erm ero err kbb kbc kbe kbk kbm kbo kbr kcb kcc kce kck kcm kcr ke- keb kec kee kek kem keo ker kkb kkc kke kkk kkm kkr kmb kmc kme kmk kmm kmo kob koc koe kok kom koo kor krc krk kro krr m-o m-r mbb mbc mbe mbk mbm mbo mbr mc- mcb mcc mce mck mcm mco mcr meb mec mee mek mem meo mer mkb mkc mke mkk mkm mko mkr mmb mmc mme mmk mmm mmo mmr mob moc moe mok mom moo mor mrb mrc mre mrk mrm mro mrr ob- obb obc obe obk obm obo obr oc- ocb occ ock ocm oco ocr oeb oec oee oem oeo oer okb okc oke okk oko okr om- omb omc ome omm omo omr oo- oob ooc ook oom ooo oor or- orb orc ore ork orm oro orr rbb rbc rbe rbk rbm rbo rbr rcb rcc rce rcm rco rcr re- reb rec ree rek rem reo rer rkb rkc rke rkk rkm rko rmb rmc rme rmm rmo rmr rob roc roe rok rom roo ror rrb rrc rrk rrm rrr