reserve x for set,
  m,n for Nat,
  a,b for Int_position,
  i,j,k for Instruction of SCMPDS,
  s,s1,s2 for State of SCMPDS,
  k1,k2 for Integer,
  loc,l for Nat,
  I,J,K for Program of SCMPDS;

theorem Th2:
  i ';' I ';' j ';' k = i ';' (I ';' j ';' k)
proof
  thus i ';' I ';' j ';' k = i ';' (I ';' j) ';' k by SCMPDS_4:15
    .= i ';' (I ';' j ';' k) by SCMPDS_4:15;
end;
