bbb bbe bbf bbi bbx be- beb bee bef bei bex bfb bfe bff bfi bfx bi- bib bie bif bii bix bxb bxi bxx ebb ebe ebf ebi ebx eeb eee eef eex ef- efb efe eff efi efx eib eie eif eii eix ex- exe exi exx fbb fbe fbf fbi fbx feb fee fef fei fex ffe fff ffi ffx fib fie fif fii fix fxe fxi fxx i-f ibb ibe ibf ibi ibx ie- iee ief iei iex ifb ife iff ifi ifx iib iie iif iii iix ixe ixi xbe xbx xee xex xfe xfx xie xii xix xxi xxx