a-a a-c aaa aac aae aan aax ac- aca acc ace acn acx aea aec aee aen aex an- ana anc ane ann anx ax- axa axe axn axx c-- caa cac cae can cax cca ccc cce ccn ccx ce- cea cec cee cen cex cn- cna cnc cne cnn cnx cxc cxx eaa eac eae ean eax ec- eca ecc ece ecn ecx eea eec eee een eex en- ena enc ene enn ex- exa exc exe exx naa nac nae nan nax nca ncc nce ncn ncx ne- nea nec nee nen nex nna nnc nne nnn nxc xaa xac xan xcx xee xen xex xna xnc xxx