a-a a-b aaa aab aad aan aax ab- aba abb abd abn abx ad- ada adb add adn adx an- ana anb and ann anx ax- axa axn axx baa bab bad ban bax bba bbb bbd bbn bbx bda bdb bdd bdx bna bnb bnd bnn bnx bxb bxd bxn bxx daa dab dad dan dax dba dbb dbd dbn dbx dda ddb ddd ddn ddx dna dnb dnd dnn dxd dxn dxx naa nab nad nan nax nba nbb nbd nbn nbx nda ndb ndd ndn nna nnb nnn nxd xaa xad xan xbx xda xdb xna xxx