a-a a-b a-c aaa aab aac aad aar aas ab- aba abb abc abd abr abs ac- aca acb acc acd acr acs ad- ada adb adc add adr ads ar- ara arb arc ard arr ars as- asa asb asc asd asr ass baa bab bac bad bar bas bba bbb bbc bbd bbr bbs bca bcb bcc bcd bcr bcs bda bdb bdc bdd bdr bds bra brb brd brr brs bsa bsb bsc bsd bsr bss c-- caa cab cac cad car cas cba cbb cbc cbd cbr cbs cca ccb ccc ccd ccr ccs cda cdb cdc cdd cdr cds cra crb crc crd crr crs csa csb csc csd csr css daa dab dac dad dar das dba dbb dbc dbd dbr dbs dca dcb dcc dcd dcr dcs dda ddb ddc ddd ddr dds dra drb drc drd drr drs dsa dsb dsc dsd dsr dss ra- raa rab rac rad rar ras rba rbb rbc rbd rbr rbs rca rcb rcc rcd rcr rcs rda rdb rdc rdd rdr rds rra rrb rrc rrd rrr rrs rsa rsb rsc rsd rsr rss saa sab sac sad sar sas sba sbb sbc sbd sbr sbs sca scb scc scd scr scs sda sdb sdc sdd sdr sds sr- sra srb src srd srr srs ss- ssa ssb ssc ssd ssr sss