-er a-a a-b a-i aaa aab aae aai aar aas ab- aba abb abe abi abr abs aea aeb aee aei aer aes ai- aia aib aie aii air ais ar- ara arb are ari arr ars as- asa asb ase asi asr ass baa bab bae bai bar bas bba bbb bbe bbi bbr bbs be- bea beb bee bei ber bes bi- bia bib bie bii bir bis bra brb bre bri brr brs bsa bsb bse bsi bsr bss eaa eab eae eai ear eas eba ebb ebe ebi ebr ebs eea eeb eee eer ees eia eib eie eii eir eis era erb ere eri err ers es- esa esb ese esi esr ess ia- iaa iab iae iai iar ias iba ibb ibe ibi ibr ibs ie- iea iee iei ier ies iia iib iie iii iir iis ir- ira irb ire iri irr irs is- isa isb ise isi isr iss ra- raa rab rae rai rar ras rba rbb rbe rbi rbr rbs re- rea reb ree rei rer res ria rib rie rii rir ris rra rrb rri rrr rrs rsa rsb rse rsi rsr rss saa sab sae sai sar sas sba sbb sbe sbi sbr sbs se- sea seb see sei ser ses sia sib sie sii sir sis sr- sra srb sre sri srr srs ss- ssa ssb sse ssi ssr sss