a-a a-b aaa aab aad aao aar aas ab- aba abb abd abo abr abs ad- ada adb add ado adr ads aoa aob aod aoo aor aos ar- ara arb ard aro arr ars as- asa asb asd aso asr ass baa bab bad bao bar bas bba bbb bbd bbo bbr bbs bda bdb bdd bdo bdr bds boa bob bod boo bor bos bra brb brd bro brr brs bsa bsb bsd bso bsr bss daa dab dad dao dar das dba dbb dbd dbo dbr dbs dda ddb ddd ddo ddr dds doa dob dod doo dor dos dra drb drd dro drr drs dsa dsb dsd dso dsr dss oaa oab oad oao oar oas ob- oba obb obd obo obr obs oda odb odd odo odr ods oo- ooa oob ood ooo oor oos or- ora orb ord oro orr ors os- osa osb osd oso osr oss ra- raa rab rad rao rar ras rba rbb rbd rbo rbr rbs rda rdb rdd rdo rdr rds roa rob rod roo ror ros rra rrb rrd rrr rrs rsa rsb rsd rso rsr rss saa sab sad sao sar sas sba sbb sbd sbo sbr sbs sda sdb sdd sdo sdr sds soa sob sod soo sor sos sr- sra srb srd sro srr srs ss- ssa ssb ssd sso ssr sss