Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  z : Z
  wp : 0 = z
  H0 : ~ VSet.In (s G) (V G)
  ============================
   (z = 0)


DEBUG:Going to execute:
intros; Zify.zify_pre_hook; zify_elim_let; zify_op