-er -ic bbb bbc bbe bbi bbr bbs bcb bcc bce bci bcr bcs be- beb bec bee bei ber bes bi- bib bic bie bii bir bis brb bre bri brr brs bsb bsc bse bsi bsr bss c-- cbb cbc cbe cbi cbr cbs ccb ccc cce cci ccr ccs ce- ceb cec cee cei cer ces ci- cib cic cie cii cir cis crb crc cre cri crr crs csb csc cse csi csr css ebb ebc ebe ebi ebr ebs ec- ecb ecc ece eci ecr ecs eeb eec eee eer ees eib eic eie eii eir eis erb erc ere eri err ers es- esb esc ese esi esr ess ibb ibc ibe ibi ibr ibs icb icc ice ici icr ics ie- iec iee iei ier ies iib iic iie iii iir iis ir- irb irc ire iri irr irs is- isb isc ise isi isr iss rbb rbc rbe rbi rbr rbs rcb rcc rce rci rcr rcs re- reb rec ree rei rer res rib ric rie rii rir ris rrb rrc rri rrr rrs rsb rsc rse rsi rsr rss sbb sbc sbe sbi sbr sbs scb scc sce sci scr scs se- seb sec see sei ser ses sib sic sie sii sir sis sr- srb src sre sri srr srs ss- ssb ssc sse ssi ssr sss