-er bbb bbc bbe bbm bbo bbr bcb bcc bce bcm bco bcr be- beb bec bee bem beo ber bmb bmc bme bmm bmo bmr bob boc boe bom boo bor brb bre brm bro brr c-- cbb cbc cbe cbm cbo cbr ccb ccc cce ccm cco ccr ce- ceb cec cee cem ceo cer cmb cmc cme cmm cmo cmr co- cob coc coe com coo cor crb crc cre crm cro crr ebb ebc ebe ebm ebo ebr ec- ecb ecc ece ecm eco ecr eeb eec eee eem eeo eer em- emb emc eme emm emo emr eo- eob eoc eoe eom eoo eor erb erc ere erm ero err m-o m-r mbb mbc mbe mbm mbo mbr mc- mcb mcc mce mcm mco mcr meb mec mee mem meo mer mmb mmc mme mmm mmo mmr mob moc moe mom moo mor mrb mrc mre mrm mro mrr ob- obb obc obe obm obo obr oc- ocb occ ocm oco ocr oeb oec oee oem oeo oer om- omb omc ome omm omo omr oo- oob ooc oom ooo oor or- orb orc ore orm oro orr rbb rbc rbe rbm rbo rbr rcb rcc rce rcm rco rcr re- reb rec ree rem reo rer rmb rmc rme rmm rmo rmr rob roc roe rom roo ror rrb rrc rrm rrr