-er bbb bbc bbe bbo bbr bbs bbx bcb bcc bce bco bcr bcs bcx be- beb bec bee beo ber bes bex bob boc boe boo bor bos box brb bre bro brr brs brx bsb bsc bse bso bsr bss bsx bxb bxo bxx c-- cbb cbc cbe cbo cbr cbs cbx ccb ccc cce cco ccr ccs ccx ce- ceb cec cee ceo cer ces cex co- cob coc coe coo cor cos cox crb crc cre cro crr crs crx csb csc cse cso csr css csx cxc cxo cxr cxs cxx ebb ebc ebe ebo ebr ebs ebx ec- ecb ecc ece eco ecr ecs ecx eeb eec eee eeo eer ees eex eo- eob eoc eoe eoo eor eos erb erc ere ero err ers es- esb esc ese eso esr ess esx ex- exc exe exo exr exs exx ob- obb obc obe obo obr obs obx oc- ocb occ oco ocr ocs ocx oeb oec oee oeo oer oes oex oo- oob ooc ooo oor oos oox or- orb orc ore oro orr ors orx os- osb osc ose oso osr oss osx ox- oxb oxc oxo oxx rbb rbc rbe rbo rbr rbs rbx rcb rcc rce rco rcr rcs rcx re- reb rec ree reo rer res rex rob roc roe roo ror ros rox rrb rrc rrr rrs rsb rsc rse rso rsr rss rsx rxr rxs sbb sbc sbe sbo sbr sbs sbx scb scc sce sco scr scs scx se- seb sec see seo ser ses sex sob soc soe soo sor sos sox sr- srb src sre sro srr srs srx ss- ssb ssc sse sso ssr sss ssx sxc sxs xbc xbe xbr xbx xcb xcr xcx xee xer xes xex xoc xoo xor xos xox xrc xrx xsb xsc xss xxo xxx