Goal:
  
  G : t
  HI : invariants
  HG : acyclic_no_loop
  x : V.t
  y : V.t
  n : Z
  p : SPath (V G) x y
  Hp : sweight p = n
  z : Z
  pi : SPath (V G) y x
  Hpi : sweight pi = z
  h : V.t
  loop : SPath (VSet.union (V G) (nodes (to_pathOf pi))) h h
  H : 0 < z + n -> 0 < sweight loop
  ltb : ~ 0 < z + n
  wl : sweight loop <= 0
  ============================
   (z <= - n)


DEBUG:Going to execute:
idtac
DEBUG LTAC Evaluated term: false
Level 2: Zify.zify_convert_to_euclidean_division_equations_flag
 has value 
false