Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  y_0 : V.t
  x_0 : V.t
  Vx : VSet.In x_0 (V G)
  Vy : VSet.In y_0 (V G)
  Hxs : lsp G x_0 y_0 = None
  K : Z
  x : V.t
  k : Z
  p : SPath G (V G) x_0 x
  Hk : sweight p = k
  ============================
   (K + sweight (reduce G' (sto_G' p)) = K + k)


DEBUG:Going to execute:
rewrite weight_reduce sto_G'_weight Hk
DEBUG LTAC Evaluated term: weight_SPath_sub
DEBUG LTAC Evaluated term: weight_SPath_sub