a-a a-b a-c aaa aab aac aao aar aay ab- aba abb abc abo abr aby ac- aca acb acc aco acr acy aoa aob aoc aoo aor ar- ara arb arc aro arr ary ay- aya ayc ayo ayr baa bab bac bao bar bay bba bbb bbc bbo bbr bby bca bcb bcc bco bcr bcy boa bob boc boo bor boy bra brb bro brr bry by- bya byc byo byr c-- caa cab cac cao car cay cba cbb cbc cbo cbr cby cca ccb ccc cco ccr co- coa cob coc coo cor coy cra crb crc cro crr cry cya cyb cyc cyo cyr oaa oab oac oao oar ob- oba obb obc obo obr oby oc- oca ocb occ oco ocr oo- ooa oob ooc ooo oor or- ora orb orc oro orr ory oya oyo ra- raa rab rac rao rar ray rba rbb rbc rbo rbr rca rcb rcc rco rcr roa rob roc roo ror roy rra rrb rrc rrr ry- rya ryc ryo ryr ryy yaa yab yac yao yar yay ybc ybr yby yca ycc yco ycy yob yoc yoo yor yoy yra yrc yro yyb yyc yyy