a-a a-c aaa aac aae aao aax ac- aca acc ace aco acx aea aec aee aeo aex aoa aoc aoe aoo aox ax- axa axe axo axx c-- caa cac cae cao cax cca ccc cce cco ccx ce- cea cec cee ceo cex co- coa coc coe coo cox cxc cxo cxx eaa eac eae eao eax ec- eca ecc ece eco ecx eea eec eee eeo eex eo- eoa eoc eoe eoo ex- exa exc exe exo exx oaa oac oae oao oax oc- oca occ oco ocx oea oec oee oeo oex oo- ooa ooc ooo oox ox- oxa oxc oxo oxx xaa xac xcx xee xex xoa xoc xoo xox xxo xxx