a-a a-b a-c aaa aab aac aad aak aao aar aas ab- aba abb abc abd abk abo abr abs ac- aca acb acc acd ack aco acr acs ad- ada adb adc add adk ado adr ads aka akb akc akd akk ako akr aks aoa aob aoc aod aok aoo aor aos ar- ara arb arc ard ark aro arr ars as- asa asb asc asd ask aso asr ass baa bab bac bad bak bao bar bas bba bbb bbc bbd bbk bbo bbr bbs bca bcb bcc bcd bck bco bcr bcs bda bdb bdc bdd bdk bdo bdr bds bka bkb bkc bkk bko bkr bks boa bob boc bod bok boo bor bos bra brb brd brk bro brr brs bsa bsb bsc bsd bsk bso bsr bss c-- caa cab cac cad cak cao car cas cba cbb cbc cbd cbk cbo cbr cbs cca ccb ccc ccd cck cco ccr ccs cda cdb cdc cdd cdk cdo cdr cds cka ckb ckc ckd cko cks co- coa cob coc cod cok coo cor cos cra crb crc crd crk cro crr crs csa csb csc csd csk cso csr css daa dab dac dad dak dao dar das dba dbb dbc dbd dbk dbo dbr dbs dca dcb dcc dcd dck dco dcr dcs dda ddb ddc ddd ddk ddo ddr dds dka dkb dkc dkk dko dkr dks doa dob doc dod dok doo dor dos dra drb drc drd drk dro drr drs dsa dsb dsc dsd dsk dso dsr dss ka- kaa kab kac kad kak kao kar kas kba kbb kbc kbd kbk kbo kbr kbs kca kcb kcc kcd kck kcr kcs kda kdb kdc kdk kdo kdr kds kkb kkc kkk kkr kks koa kob koc kod kok koo kor kos kra krc krd krk kro krr krs ksa ksb ksc ksd ksk kso ksr kss oaa oab oac oad oak oao oar oas ob- oba obb obc obd obk obo obr obs oc- oca ocb occ ocd ock oco ocr ocs oda odb odc odd odo odr ods oka okb okc okd okk oko okr oks oo- ooa oob ooc ood ook ooo oor oos or- ora orb orc ord ork oro orr ors os- osa osb osc osd osk oso osr oss ra- raa rab rac rad rak rao rar ras rba rbb rbc rbd rbk rbo rbr rbs rca rcb rcc rcd rco rcr rcs rda rdb rdc rdd rdo rdr rds rkb rkc rkk rko rks roa rob roc rod rok roo ror ros rra rrb rrc rrd rrk rrr rrs rsa rsb rsc rsd rsk rso rsr rss saa sab sac sad sak sao sar sas sba sbb sbc sbd sbk sbo sbr sbs sca scb scc scd sck sco scr scs sda sdb sdc sdd sdk sdo sdr sds sk- ska skb skc skd skk sko skr sks soa sob soc sod sok soo sor sos sr- sra srb src srd srk sro srr srs ss- ssa ssb ssc ssd ssk sso ssr sss