reserve x,y,z,c for object,
  f for Function of 2-tuples_on BOOLEAN, BOOLEAN;
reserve s for State of 2GatesCircuit(x,y,c,f);

theorem
  for x,y,c being non pair object holds InputVertices
  BitAdderWithOverflowStr(x,y,c) is without_pairs
proof
  let x,y,c be non pair object;
  InputVertices BitAdderWithOverflowStr(x,y,c) = {x,y,c} by Th85;
  hence thesis;
end;
