a-a a-b a-c a-t aaa aab aac aao aar aas aat ab- aba abb abc abo abr abs abt ac- aca acb acc aco acr acs act aoa aob aoc aoo aor aos aot ar- ara arb arc aro arr ars art as- asa asb asc aso asr ass ast at- ata atb atc ato atr ats att baa bab bac bao bar bas bat bba bbb bbc bbo bbr bbs bbt bca bcb bcc bco bcr bcs bct boa bob boc boo bor bos bot bra brb bro brr brs brt bsa bsb bsc bso bsr bss bst bta btb btc bto btr bts btt c-- caa cab cac cao car cas cat cba cbb cbc cbo cbr cbs cbt cca ccb ccc cco ccr ccs cct co- coa cob coc coo cor cos cot cra crb crc cro crr crs crt csa csb csc cso csr css cst cta ctb ctc cto ctr cts ctt oaa oab oac oao oar oas oat ob- oba obb obc obo obr obs obt oc- oca ocb occ oco ocr ocs oct oo- ooa oob ooc ooo oor oos oot or- ora orb orc oro orr ors ort os- osa osb osc oso osr oss ost ot- ota otb otc oto otr ots ott ra- raa rab rac rao rar ras rat rba rbb rbc rbo rbr rbs rbt rca rcb rcc rco rcr rcs rct roa rob roc roo ror ros rot rra rrb rrc rrr rrs rrt rsa rsb rsc rso rsr rss rst rta rtb rtc rto rtr rts rtt saa sab sac sao sar sas sat sba sbb sbc sbo sbr sbs sbt sca scb scc sco scr scs sct soa sob soc soo sor sos sot sr- sra srb src sro srr srs srt ss- ssa ssb ssc sso ssr sss sst sta stb stc sto str sts stt taa tab tac tao tar tas tat tba tbb tbc tbo tbr tbs tbt tca tcb tcc tco tcr tcs tct to- toa tob toc too tor tos tot tra trb trc tro trr trs trt tsa tsb tsc tso tsr tss tst tta ttb ttc tto ttr tts ttt