a-a a-b a-c aaa aab aac aan aao aax aay ab- aba abb abc abn abo abx aby ac- aca acb acc acn aco acx acy an- ana anb anc ann ano anx any aoa aob aoc aon aoo aox ax- axa axn axo axx ay- aya ayc ayn ayo ayx baa bab bac ban bao bax bay bba bbb bbc bbn bbo bbx bby bca bcb bcc bcn bco bcx bcy bna bnb bnc bnn bno bnx boa bob boc bon boo box boy bxb bxn bxo bxx by- bya byc byn byo c-- caa cab cac can cao cax cay cba cbb cbc cbn cbo cbx cby cca ccb ccc ccn cco ccx cn- cna cnb cnc cnn cno cnx cny co- coa cob coc con coo cox coy cxc cxo cxx cya cyb cyc cyn cyo naa nab nac nan nao nax nay nba nbb nbc nbn nbo nbx nca ncb ncc ncn nco ncx nna nnb nnc nnn nno no- noa nob noc non noo nox noy nxc nya nyc nyn nyo nyx nyy oaa oab oac oan oao oax ob- oba obb obc obn obo obx oby oc- oca ocb occ ocn oco ocx on- ona onb onc onn ono onx ony oo- ooa oob ooc oon ooo oox ox- oxa oxb oxc oxn oxo oxx oxy oya oyo xaa xac xan xbc xbx xcb xcx xna xnc xno xoa xoc xon xoo xox xxo xxx xxy xyy yaa yab yac yan yao yax yay ybc yby yca ycc yco ycy yna ynn yny yob yoc yon yoo yox yoy yxa yxy yyb yyc yyy