a-a a-b aaa aab aad aae aax ab- aba abb abd abe abx ad- ada adb add ade adx aea aeb aed aee aex ax- axa axe axx baa bab bad bae bax bba bbb bbd bbe bbx bda bdb bdd bde bdx be- bea beb bed bee bex bxb bxd bxx daa dab dad dae dax dba dbb dbd dbe dbx dda ddb ddd dde ddx de- dea deb ded dee dex dxd dxx eaa eab ead eae eax eba ebb ebd ebe ebx ed- eda edb edd ede edx eea eeb eed eee eex ex- exa exd exe exx xaa xad xbe xbx xda xdb xde xed xee xex xxx