-er a-a a-b aaa aab aae aar aas ab- aba abb abe abr abs aea aeb aee aer aes ar- ara arb are arr ars as- asa asb ase asr ass baa bab bae bar bas bba bbb bbe bbr bbs be- bea beb bee ber bes bra brb bre brr brs bsa bsb bse bsr bss eaa eab eae ear eas eba ebb ebe ebr ebs eea eeb eee eer ees era erb ere err ers es- esa esb ese esr ess ra- raa rab rae rar ras rba rbb rbe rbr rbs re- rea reb ree rer res rra rrb rrr rrs rsa rsb rse rsr rss saa sab sae sar sas sba sbb sbe sbr sbs se- sea seb see ser ses sr- sra srb sre srr srs ss- ssa ssb sse ssr sss