. simp only [List.mem_pmap, not_exists]
  intro a ha hcntr
  cases Fin.restrict_inj _ _ hcntr.2
  exact absurd hcntr.1 <| pivot_not_mem_path i j
m n : Nat
i : Fin m
j : Fin n
⊢ ¬Fin.restrict (Board.pivot i j) (_ : ↑(Board.pivot i j) < (m + 1) * (n + 1) - 1) ∈
      List.pmap Fin.restrict (Board.path i j)
        (_ : ∀ (a : Fin ((m + 1) * (n + 1))), a ∈ Board.path i j → ↑a < (m + 1) * (n + 1) - 1)
no goals