theorem Th12:
 card(i ';' j) = 3
  proof
   thus card(i ';' j) = card Macro i + card Macro j - 1 by COMPOS_1:20
      .= 2 + card Macro i - 1 by COMPOS_1:56
      .= 2 + 2 - 1 by COMPOS_1:56
      .= 3;
  end;
