-er -ol bbb bbc bbe bbk bbl bbo bbr bbs bcb bcc bce bck bcl bco bcr bcs be- beb bec bee bek bel beo ber bes bkb bkc bke bkk bkl bko bkr bks blb blc ble blk bll blo blr bls bob boc boe bok bol boo bor bos brb bre brk brl bro brr brs bsb bsc bse bsk bsl bso bsr bss c-- cbb cbc cbe cbk cbl cbo cbr cbs ccb ccc cce cck ccl cco ccr ccs ce- ceb cec cee cek cel ceo cer ces ckb ckc cko cks cl- clb clc cle clk cll clo clr cls co- cob coc coe cok col coo cor cos crb crc cre crk crl cro crr crs csb csc cse csk csl cso csr css ebb ebc ebe ebk ebl ebo ebr ebs ec- ecb ecc ece eck ecl eco ecr ecs eeb eec eee eek eel eeo eer ees ekb ekc eke ekl eko ekr eks elb elc ele elk ell elo elr els eo- eob eoc eoe eok eol eoo eor eos erb erc ere erk erl ero err ers es- esb esc ese esk esl eso esr ess kbb kbc kbe kbk kbl kbo kbr kbs kcb kcc kce kck kcl kcr kcs ke- keb kec kee kek kel keo ker kes kkb kkc kke kkk kkl kkr kks kl- klb klc klo klr kls kob koc koe kok kol koo kor kos krc krk krl kro krr krs ksb ksc kse ksk ksl kso ksr kss lbb lbc lbe lbk lbl lbo lbr lbs lcb lcc lce lck lcl lco lcr lcs leb lec lee lek lel leo ler les lkb lkl lkr lks llb llc lle llk lll llo llr lls lob loc loe lok lol loo lor los lrb lrc lrk lro lrr lrs lsb lsc lse lsk lsl lso lsr lss ob- obb obc obe obk obl obo obr obs oc- ocb occ ock ocl oco ocr ocs oeb oec oee oel oeo oer oes okb okc oke okk okl oko okr oks olb olc ole olk oll olo ols oo- oob ooc ook ool ooo oor oos or- orb orc ore ork orl oro orr ors os- osb osc ose osk osl oso osr oss rbb rbc rbe rbk rbl rbo rbr rbs rcb rcc rce rcl rco rcr rcs re- reb rec ree rek rel reo rer res rkb rkc rke rkk rko rks rlc rle rll rlo rlr rls rob roc roe rok rol roo ror ros rrb rrc rrk rrl rrr rrs rsb rsc rse rsk rsl rso rsr rss sbb sbc sbe sbk sbl sbo sbr sbs scb scc sce sck scl sco scr scs se- seb sec see sek sel seo ser ses sk- skb skc ske skk skl sko skr sks slb slc sle slk sll slo slr sls sob soc soe sok sol soo sor sos sr- srb src sre srk srl sro srr srs ss- ssb ssc sse ssk ssl sso ssr sss