text: input = """
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %
  % dlv-Interpreter for preferred answer sets of propositional programs. 
  % 
  % Store rules
  %  
  %     r:  A <- B1,...,Bm, not C1,..., not Cn
  %
  % by facts: 
  % 
  %  rule(r). head(A,r). bpl(B1,r). ... bpl(Bm,r). nbl(C1,r). ... nbl(Cn,r).
  %
  % classical negation must be emulated, state facts opp(L,L') for
  % opposite classical literals 
  %
  % Specify preference  r < r' through fact  pr(r,r'). 
  %
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  % Apply rules of the program: 
  
    in_AS(X) :- head(X,Y), not pos_body_false(Y), not neg_body_false(Y). 
  
  % pbl - positive body literal; nbl - negative body literal 
  
    pos_body_false(Y) :- pbl(X,Y), not in_AS(X). 
    neg_body_false(Y) :- nbl(X,Y), in_AS(X). 
  
  % Eliminate opposite literals (explicitly specified).
  
    :- opp(X,Y), in_AS(X), in_AS(Y).
  
  
  """
  output = """
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  %
  % dlv-Interpreter for preferred answer sets of propositional programs. 
  % 
  % Store rules
  %  
  %     r:  A <- B1,...,Bm, not C1,..., not Cn
  %
  % by facts: 
  % 
  %  rule(r). head(A,r). bpl(B1,r). ... bpl(Bm,r). nbl(C1,r). ... nbl(Cn,r).
  %
  % classical negation must be emulated, state facts opp(L,L') for
  % opposite classical literals 
  %
  % Specify preference  r < r' through fact  pr(r,r'). 
  %
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  
  % Apply rules of the program: 
  
    in_AS(X) :- head(X,Y), not pos_body_false(Y), not neg_body_false(Y). 
  
  % pbl - positive body literal; nbl - negative body literal 
  
    pos_body_false(Y) :- pbl(X,Y), not in_AS(X). 
    neg_body_false(Y) :- nbl(X,Y), in_AS(X). 
  
  % Eliminate opposite literals (explicitly specified).
  
    :- opp(X,Y), in_AS(X), in_AS(Y).
  
  
  """
  