
theorem SAB:
  for a,b be Integer holds
  a + b = 2*((a div 2) + (b div 2)) + (parity a) + (parity b)
  proof
    let a,b be Integer;
    a = (a div 2)*2 + (a mod 2) & b = (b div 2)*2 + (b mod 2) by INT_1:59;
    hence thesis;
  end;
