-er bbb bbc bbe bbk bbn bbr bbs bcb bcc bce bck bcn bcr bcs be- beb bec bee bek ben ber bes bkb bkc bke bkk bkn bkr bks bnb bnc bne bnk bnn bnr bns brb bre brk brn brr brs bsb bsc bse bsk bsn bsr bss c-- cbb cbc cbe cbk cbn cbr cbs ccb ccc cce cck ccn ccr ccs ce- ceb cec cee cek cen cer ces ckb ckc cks cn- cnb cnc cne cnn cnr cns crb crc cre crk crn crr crs csb csc cse csk csn csr css ebb ebc ebe ebk ebn ebr ebs ec- ecb ecc ece eck ecn ecr ecs eeb eec eee eek een eer ees ekb ekc eke ekr eks en- enb enc ene enk enn enr ens erb erc ere erk ern err ers es- esb esc ese esk esn esr ess kbb kbc kbe kbk kbn kbr kbs kcb kcc kce kck kcn kcr kcs ke- keb kec kee kek ken ker kes kkb kkc kke kkk kkn kkr kks kn- knc kne knk knn knr krc krk krn krr krs ksb ksc kse ksk ksn ksr kss nbb nbc nbe nbk nbn nbr nbs ncb ncc nce nck ncn ncr ncs ne- neb nec nee nek nen ner nes nkc nke nkk nkn nkr nks nnb nnc nne nnk nnn nns nrb nrc nre nrk nrn nrr nrs nsb nsc nse nsk nsn nsr nss rbb rbc rbe rbk rbn rbr rbs rcb rcc rce rcn rcr rcs re- reb rec ree rek ren rer res rkb rkc rke rkk rks rnb rnc rnn rnr rns rrb rrc rrk rrn rrr rrs rsb rsc rse rsk rsn rsr rss sbb sbc sbe sbk sbn sbr sbs scb scc sce sck scn scr scs se- seb sec see sek sen ser ses sk- skb skc ske skk skr sks snb snc sne snk snn snr sns sr- srb src sre srk srn srr srs ss- ssb ssc sse ssk ssn ssr sss