a-a a-b a-c aaa aab aac aad aao aar aas ab- aba abb abc abd abo abr abs ac- aca acb acc acd aco acr acs ad- ada adb adc add ado adr ads aoa aob aoc aod aoo aor aos ar- ara arb arc ard aro arr ars as- asa asb asc asd aso asr ass baa bab bac bad bao bar bas bba bbb bbc bbd bbo bbr bbs bca bcb bcc bcd bco bcr bcs bda bdb bdc bdd bdo bdr bds boa bob boc bod boo bor bos bra brb brd bro brr brs bsa bsb bsc bsd bso bsr bss c-- caa cab cac cad cao car cas cba cbb cbc cbd cbo cbr cbs cca ccb ccc ccd cco ccr ccs cda cdb cdc cdd cdo cdr cds co- coa cob coc cod coo cor cos cra crb crc crd cro crr crs csa csb csc csd cso csr css daa dab dac dad dao dar das dba dbb dbc dbd dbo dbr dbs dca dcb dcc dcd dco dcr dcs dda ddb ddc ddd ddo ddr dds doa dob doc dod doo dor dos dra drb drc drd dro drr drs dsa dsb dsc dsd dso dsr dss oaa oab oac oad oao oar oas ob- oba obb obc obd obo obr obs oc- oca ocb occ ocd oco ocr ocs oda odb odc odd odo odr ods oo- ooa oob ooc ood ooo oor oos or- ora orb orc ord oro orr ors os- osa osb osc osd oso osr oss ra- raa rab rac rad rao rar ras rba rbb rbc rbd rbo rbr rbs rca rcb rcc rcd rco rcr rcs rda rdb rdc rdd rdo rdr rds roa rob roc rod roo ror ros rra rrb rrc rrd rrr rrs rsa rsb rsc rsd rso rsr rss saa sab sac sad sao sar sas sba sbb sbc sbd sbo sbr sbs sca scb scc scd sco scr scs sda sdb sdc sdd sdo sdr sds soa sob soc sod soo sor sos sr- sra srb src srd sro srr srs ss- ssa ssb ssc ssd sso ssr sss