Goal:
  
  G : t
  x : V.t
  y : V.t
  p : PathOf G x y
  q : PathOf G y x
  _view_subject_ : weight p + weight q <= 0
  ============================
   (weight p <= - weight q)


DEBUG:Going to execute:
<coq-core.plugins.micromega::Lia@0> $1