a-a a-b a-c a-t aaa aab aac aao aas aat aay ab- aba abb abc abo abs abt aby ac- aca acb acc aco acs act acy aoa aob aoc aoo aos aot as- asa asb asc aso ass ast asy at- ata atb atc ato ats att ay- aya ayc ayo ays ayt baa bab bac bao bas bat bay bba bbb bbc bbo bbs bbt bby bca bcb bcc bco bcs bct bcy boa bob boc boo bos bot boy bsa bsb bsc bso bss bst bsy bta btb btc bto bts btt bty by- bya byc byo bys byt c-- caa cab cac cao cas cat cay cba cbb cbc cbo cbs cbt cby cca ccb ccc cco ccs cct co- coa cob coc coo cos cot coy csa csb csc cso css cst csy cta ctb ctc cto cts ctt cty cya cyb cyc cyo cys cyt oaa oab oac oao oas oat ob- oba obb obc obo obs obt oby oc- oca ocb occ oco ocs oct oo- ooa oob ooc ooo oos oot os- osa osb osc oso oss ost ot- ota otb otc oto ots ott oya oyo oys saa sab sac sao sas sat say sba sbb sbc sbo sbs sbt sby sca scb scc sco scs sct soa sob soc soo sos sot soy ss- ssa ssb ssc sso sss sst sta stb stc sto sts stt sty sy- sya syb syc sys syt taa tab tac tao tas tat tay tba tbb tbc tbo tbs tbt tca tcb tcc tco tcs tct to- toa tob toc too tos tot toy tsa tsb tsc tso tss tst tsy tta ttb ttc tto tts ttt tty tya tyc tyo tys tyt yaa yab yac yao yas yat yay ybc ybs yby yca ycc yco ycs ycy yob yoc yoo yos yot yoy ysa ysb ysc yso yss yst ysy yta ytc yto yts ytt yyb yyc yys yyt yyy