a-a a-b aaa aab aae aas aax ab- aba abb abe abs abx aea aeb aee aes aex as- asa asb ase ass asx ax- axa axe axs axx baa bab bae bas bax bba bbb bbe bbs bbx be- bea beb bee bes bex bsa bsb bse bss bsx bxb bxx eaa eab eae eas eax eba ebb ebe ebs ebx eea eeb eee ees eex es- esa esb ese ess esx ex- exa exe exs exx saa sab sae sas sax sba sbb sbe sbs sbx se- sea seb see ses sex ss- ssa ssb sse sss ssx sxs xaa xas xbe xbx xee xes xex xsa xsb xss xxx