Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  n : Z
  x : V.t
  Hle : leq_vertices G n x x
  Vy : VSet.In x (V G)
  Vx : ~ VSet.In x (V G)
  Hx : x = x
  XX : Z.of_nat
         (if is_left (left Hx)
          then
           if n <=? 0
           then (Z.to_nat (Z.of_nat (to_label (lsp G (s G) x)) - n) + 1)%nat
           else to_label (lsp G (s G) x)
          else to_label (lsp G (s G) x)) + n <=
       Z.of_nat
         (if is_left (left eq_refl)
          then
           if n <=? 0
           then (Z.to_nat (Z.of_nat (to_label (lsp G (s G) x)) - n) + 1)%nat
           else to_label (lsp G (s G) x)
          else to_label (lsp G (s G) x))
  ============================
   False


DEBUG:Going to execute:
let rec do_ccl :=
            try do_atom; repeat (do_intro; try do_atom); try arith_congr;
             (solve [ split; do_ccl ])
           in
           (solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"