a-a a-b a-c aaa aab aac aao aar aas aay ab- aba abb abc abo abr abs aby ac- aca acb acc aco acr acs acy aoa aob aoc aoo aor aos ar- ara arb arc aro arr ars ary as- asa asb asc aso asr ass asy ay- aya ayc ayo ayr ays baa bab bac bao bar bas bay bba bbb bbc bbo bbr bbs bby bca bcb bcc bco bcr bcs bcy boa bob boc boo bor bos boy bra brb bro brr brs bry bsa bsb bsc bso bsr bss bsy by- bya byc byo byr bys c-- caa cab cac cao car cas cay cba cbb cbc cbo cbr cbs cby cca ccb ccc cco ccr ccs co- coa cob coc coo cor cos coy cra crb crc cro crr crs cry csa csb csc cso csr css csy cya cyb cyc cyo cyr cys oaa oab oac oao oar oas ob- oba obb obc obo obr obs oby oc- oca ocb occ oco ocr ocs oo- ooa oob ooc ooo oor oos or- ora orb orc oro orr ors ory os- osa osb osc oso osr oss oya oyo oys ra- raa rab rac rao rar ras ray rba rbb rbc rbo rbr rbs rca rcb rcc rco rcr rcs roa rob roc roo ror ros roy rra rrb rrc rrr rrs rsa rsb rsc rso rsr rss ry- rya ryc ryo ryr rys ryy saa sab sac sao sar sas say sba sbb sbc sbo sbr sbs sby sca scb scc sco scr scs soa sob soc soo sor sos soy sr- sra srb src sro srr srs sry ss- ssa ssb ssc sso ssr sss sy- sya syb syc syr sys yaa yab yac yao yar yas yay ybc ybr ybs yby yca ycc yco ycs ycy yob yoc yoo yor yos yoy yra yrc yro yrs ysa ysb ysc yso ysr yss ysy yyb yyc yys yyy