a-a a-b a-c aaa aab aac aan aao aar aay ab- aba abb abc abn abo abr aby ac- aca acb acc acn aco acr acy an- ana anb anc ann ano anr any aoa aob aoc aon aoo aor ar- ara arb arc arn aro arr ary ay- aya ayc ayn ayo ayr baa bab bac ban bao bar bay bba bbb bbc bbn bbo bbr bby bca bcb bcc bcn bco bcr bcy bna bnb bnc bnn bno bnr boa bob boc bon boo bor boy bra brb brn bro brr bry by- bya byc byn byo byr c-- caa cab cac can cao car cay cba cbb cbc cbn cbo cbr cby cca ccb ccc ccn cco ccr cn- cna cnb cnc cnn cno cnr cny co- coa cob coc con coo cor coy cra crb crc crn cro crr cry cya cyb cyc cyn cyo cyr naa nab nac nan nao nar nay nba nbb nbc nbn nbo nbr nca ncb ncc ncn nco ncr nna nnb nnc nnn nno no- noa nob noc non noo nor noy nra nrb nrc nrn nro nrr nry nya nyc nyn nyo nyy oaa oab oac oan oao oar ob- oba obb obc obn obo obr oby oc- oca ocb occ ocn oco ocr on- ona onb onc onn ono onr ony oo- ooa oob ooc oon ooo oor or- ora orb orc orn oro orr ory oya oyo ra- raa rab rac ran rao rar ray rba rbb rbc rbn rbo rbr rca rcb rcc rcn rco rcr rna rnb rnc rnn rno rnr rny roa rob roc ron roo ror roy rra rrb rrc rrn rrr ry- rya ryc ryn ryo ryr ryy yaa yab yac yan yao yar yay ybc ybr yby yca ycc yco ycy yna ynn yny yob yoc yon yoo yor yoy yra yrc yrn yro yyb yyc yyy