-er a-a a-b aaa aab aae aao aar aas ab- aba abb abe abo abr abs aea aeb aee aeo aer aes aoa aob aoe aoo aor aos ar- ara arb are aro arr ars as- asa asb ase aso asr ass baa bab bae bao bar bas bba bbb bbe bbo bbr bbs be- bea beb bee beo ber bes boa bob boe boo bor bos bra brb bre bro brr brs bsa bsb bse bso bsr bss eaa eab eae eao ear eas eba ebb ebe ebo ebr ebs eea eeb eee eeo eer ees eo- eoa eob eoe eoo eor eos era erb ere ero err ers es- esa esb ese eso esr ess oaa oab oae oao oar oas ob- oba obb obe obo obr obs oea oeb oee oeo oer oes oo- ooa oob ooo oor oos or- ora orb ore oro orr ors os- osa osb ose oso osr oss ra- raa rab rae rao rar ras rba rbb rbe rbo rbr rbs re- rea reb ree reo rer res roa rob roe roo ror ros rra rrb rrr rrs rsa rsb rse rso rsr rss saa sab sae sao sar sas sba sbb sbe sbo sbr sbs se- sea seb see seo ser ses soa sob soe soo sor sos sr- sra srb sre sro srr srs ss- ssa ssb sse sso ssr sss