Definition prog_c : com :=
  SKIP.Definition prog_g : com :=
  WHILE BTrue DO
    SKIP
  END.Definition equiv_classes : list (list com)
  (* REPLACE THIS LINE WITH ":= _your_definition_ ." *).

Lemma sym_cequiv : forall (c1 c2 : com), cequiv c1 c2 -> cequiv c2 c1.