-er bbb bbc bbe bbn bbr bbs bcb bcc bce bcn bcr bcs be- beb bec bee ben ber bes bnb bnc bne bnn bnr bns brb bre brn brr brs bsb bsc bse bsn bsr bss c-- cbb cbc cbe cbn cbr cbs ccb ccc cce ccn ccr ccs ce- ceb cec cee cen cer ces cn- cnb cnc cne cnn cnr cns crb crc cre crn crr crs csb csc cse csn csr css ebb ebc ebe ebn ebr ebs ec- ecb ecc ece ecn ecr ecs eeb eec eee een eer ees en- enb enc ene enn enr ens erb erc ere ern err ers es- esb esc ese esn esr ess nbb nbc nbe nbn nbr nbs ncb ncc nce ncn ncr ncs ne- neb nec nee nen ner nes nnb nnc nne nnn nns nrb nrc nre nrn nrr nrs nsb nsc nse nsn nsr nss rbb rbc rbe rbn rbr rbs rcb rcc rce rcn rcr rcs re- reb rec ree ren rer res rnb rnc rnn rnr rns rrb rrc rrn rrr rrs rsb rsc rse rsn rsr rss sbb sbc sbe sbn sbr sbs scb scc sce scn scr scs se- seb sec see sen ser ses snb snc sne snn snr sns sr- srb src sre srn srr srs ss- ssb ssc sse ssn ssr sss