a-a a-b aaa aab aad aar aas ab- aba abb abd abr abs ad- ada adb add adr ads ar- ara arb ard arr ars as- asa asb asd asr ass baa bab bad bar bas bba bbb bbd bbr bbs bda bdb bdd bdr bds bra brb brd brr brs bsa bsb bsd bsr bss daa dab dad dar das dba dbb dbd dbr dbs dda ddb ddd ddr dds dra drb drd drr drs dsa dsb dsd dsr dss ra- raa rab rad rar ras rba rbb rbd rbr rbs rda rdb rdd rdr rds rra rrb rrd rrr rrs rsa rsb rsd rsr rss saa sab sad sar sas sba sbb sbd sbr sbs sda sdb sdd sdr sds sr- sra srb srd srr srs ss- ssa ssb ssd ssr sss