-er bbb bbc bbe bbh bbk bbo bbr bbs bcb bcc bce bch bck bco bcr bcs be- beb bec bee beh bek beo ber bes bhb bhc bhe bhh bhk bho bhr bhs bkb bkc bke bkk bko bkr bks bob boc boe boh bok boo bor bos brb bre brh brk bro brr brs bsb bsc bse bsh bsk bso bsr bss c-- cbb cbc cbe cbh cbk cbo cbr cbs ccb ccc cce cch cck cco ccr ccs ce- ceb cec cee ceh cek ceo cer ces ch- chb chc che chh chk cho chr chs ckb ckc ckh cko cks co- cob coc coe coh cok coo cor cos crb crc cre crh crk cro crr crs csb csc cse csh csk cso csr css ebb ebc ebe ebh ebk ebo ebr ebs ec- ecb ecc ece ech eck eco ecr ecs eeb eec eee eek eeo eer ees ehb ehc ehe ehh eho ehr ehs ekb ekc eke ekh eko ekr eks eo- eob eoc eoe eoh eok eoo eor eos erb erc ere erh erk ero err ers es- esb esc ese esh esk eso esr ess hbb hbc hbe hbh hbk hbo hbr hbs hcb hcc hce hch hck hco hcr hcs he- heb hec hee heh hek heo her hes hhb hhc hhe hhh hhk hho hhr hhs hkb hkh hkk hko hkr hks hob hoc hoe hoh hok hoo hor hos hr- hrb hrc hre hrh hrk hro hrr hrs hsb hsc hse hsh hsk hsr hss kbb kbc kbe kbh kbk kbo kbr kbs kcb kcc kce kch kck kcr kcs ke- keb kec kee keh kek keo ker kes khe khh khk kho khr khs kkb kkc kke kkh kkk kkr kks kob koc koe koh kok koo kor kos krc krk kro krr krs ksb ksc kse ksh ksk kso ksr kss ob- obb obc obe obh obk obo obr obs oc- ocb occ och ock oco ocr ocs oeb oec oee oeh oeo oer oes ohc ohe ohh oho ohr ohs okb okc oke okk oko okr oks oo- oob ooc ooh ook ooo oor oos or- orb orc ore orh ork oro orr ors os- osb osc ose osh osk oso osr oss rbb rbc rbe rbh rbk rbo rbr rbs rcb rcc rce rch rco rcr rcs re- reb rec ree reh rek reo rer res rh- rhb rhc rhe rhh rho rhr rhs rkb rkc rke rkk rko rks rob roc roe roh rok roo ror ros rrb rrc rrh rrk rrr rrs rsb rsc rse rsh rsk rso rsr rss sbb sbc sbe sbh sbk sbo sbr sbs scb scc sce sch sck sco scr scs se- seb sec see seh sek seo ser ses sh- shb shc she shh shk sho shr shs sk- skb skc ske skh skk sko skr sks sob soc soe soh sok soo sor sos sr- srb src sre srh srk sro srr srs ss- ssb ssc sse ssh ssk sso ssr sss