Goal:
  
  s : VSet.t
  x : V.t
  Hx : Datatypes.S (VSet.cardinal (VSet.remove x s)) = VSet.cardinal s
  ============================
   (VSet.cardinal (VSet.remove x s) < VSet.cardinal s)%nat


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