-er bbb bbc bbe bbm bbo bbr bbs bcb bcc bce bcm bco bcr bcs be- beb bec bee bem beo ber bes bmb bmc bme bmm bmo bmr bms bob boc boe bom boo bor bos brb bre brm bro brr brs bsb bsc bse bsm bso bsr bss c-- cbb cbc cbe cbm cbo cbr cbs ccb ccc cce ccm cco ccr ccs ce- ceb cec cee cem ceo cer ces cmb cmc cme cmm cmo cmr cms co- cob coc coe com coo cor cos crb crc cre crm cro crr crs csb csc cse csm cso csr css ebb ebc ebe ebm ebo ebr ebs ec- ecb ecc ece ecm eco ecr ecs eeb eec eee eem eeo eer ees em- emb emc eme emm emo emr ems eo- eob eoc eoe eom eoo eor eos erb erc ere erm ero err ers es- esb esc ese esm eso esr ess m-o m-r mbb mbc mbe mbm mbo mbr mbs mc- mcb mcc mce mcm mco mcr mcs meb mec mee mem meo mer mes mmb mmc mme mmm mmo mmr mms mob moc moe mom moo mor mos mrb mrc mre mrm mro mrr mrs msb msc mse msm mso msr mss ob- obb obc obe obm obo obr obs oc- ocb occ ocm oco ocr ocs oeb oec oee oem oeo oer oes om- omb omc ome omm omo omr oms oo- oob ooc oom ooo oor oos or- orb orc ore orm oro orr ors os- osb osc ose osm oso osr oss rbb rbc rbe rbm rbo rbr rbs rcb rcc rce rcm rco rcr rcs re- reb rec ree rem reo rer res rmb rmc rme rmm rmo rmr rms rob roc roe rom roo ror ros rrb rrc rrm rrr rrs rsb rsc rse rsm rso rsr rss sbb sbc sbe sbm sbo sbr sbs scb scc sce scm sco scr scs se- seb sec see sem seo ser ses smb smc sme smm smo smr sms sob soc soe som soo sor sos sr- srb src sre srm sro srr srs ss- ssb ssc sse ssm sso ssr sss