-er bbb bbc bbe bbg bbo bbr bbs bcb bcc bce bcg bco bcr bcs be- beb bec bee beg beo ber bes bgb bgc bge bgg bgo bgr bgs bob boc boe bog boo bor bos brb bre brg bro brr brs bsb bsc bse bsg bso bsr bss c-- cbb cbc cbe cbg cbo cbr cbs ccb ccc cce ccg cco ccr ccs ce- ceb cec cee ceg ceo cer ces cgb cgc cge cgg cgo cgr cgs co- cob coc coe cog coo cor cos crb crc cre crg cro crr crs csb csc cse csg cso csr css ebb ebc ebe ebg ebo ebr ebs ec- ecb ecc ece ecg eco ecr ecs eeb eec eee eeg eeo eer ees egb egc ege egg ego egr egs eo- eob eoc eoe eog eoo eor eos erb erc ere erg ero err ers es- esb esc ese esg eso esr ess gbc gbe gbg gbo gbr gbs gcb gcc gce gcg gco gcr gcs ge- geb gec gee geg geo ger ges ggb ggc ggg ggo ggr ggs gob goc goe gog goo gor gos grb grc gre grg gro grr grs gsb gsc gse gsg gso gsr gss ob- obb obc obe obg obo obr obs oc- ocb occ ocg oco ocr ocs oeb oec oee oeg oeo oer oes ogc oge ogg ogo ogs oo- oob ooc oog ooo oor oos or- orb orc ore org oro orr ors os- osb osc ose osg oso osr oss rbb rbc rbe rbg rbo rbr rbs rcb rcc rce rcg rco rcr rcs re- reb rec ree reg reo rer res rgb rgc rge rgg rgo rgr rgs rob roc roe rog roo ror ros rrb rrc rrg rrr rrs rsb rsc rse rsg rso rsr rss sbb sbc sbe sbg sbo sbr sbs scb scc sce scg sco scr scs se- seb sec see seg seo ser ses sgb sgc sge sgg sgo sgr sgs sob soc soe sog soo sor sos sr- srb src sre srg sro srr srs ss- ssb ssc sse ssg sso ssr sss