a-a a-b a-c aaa aab aac aan aar aay ab- aba abb abc abn abr aby ac- aca acb acc acn acr acy an- ana anb anc ann anr any ar- ara arb arc arn arr ary ay- aya ayc ayn ayr baa bab bac ban bar bay bba bbb bbc bbn bbr bby bca bcb bcc bcn bcr bcy bna bnb bnc bnn bnr bra brb brn brr bry by- bya byc byn byr c-- caa cab cac can car cay cba cbb cbc cbn cbr cby cca ccb ccc ccn ccr cn- cna cnb cnc cnn cnr cny cra crb crc crn crr cry cya cyb cyc cyn cyr naa nab nac nan nar nay nba nbb nbc nbn nbr nca ncb ncc ncn ncr nna nnb nnc nnn nra nrb nrc nrn nrr nry nya nyc nyn nyy ra- raa rab rac ran rar ray rba rbb rbc rbn rbr rca rcb rcc rcn rcr rna rnb rnc rnn rnr rny rra rrb rrc rrn rrr ry- rya ryc ryn ryr ryy yaa yab yac yan yar yay ybc ybr yby yca ycc ycy yna ynn yny yra yrc yrn yyb yyc yyy