reserve x for Int_position,
  n,p0 for Nat;
reserve P,Q,V for Instruction-Sequence of SCMPDS;

theorem Th4:
  for i1,i2,i3,i4 be Instruction of SCMPDS holds
  card (i1 ';' i2 ';' i3 ';' i4) = 4
proof
  let x1,x2,x3,x4 be Instruction of SCMPDS;
  thus card (x1 ';' x2 ';' x3 ';' x4)=card (x1 ';' x2 ';' x3)+1 by SCMP_GCD:4
    .=card (x1 ';' x2 )+1+1 by SCMP_GCD:4
    .=2+1+1 by SCMP_GCD:5
    .=4;
end;
