exact ⟨
  pivot_not_mem_pathL i j,
  pivot_not_mem_pathB i j,
  pivot_not_mem_pathR i j,
  pivot_not_mem_pathT i j
⟩
m n : Nat
i : Fin m
j : Fin n
⊢ ¬Board.pivot i j ∈ Board.pathL i j ∧
    ¬Board.pivot i j ∈ Board.pathB n i ∧ ¬Board.pivot i j ∈ Board.pathR m j ∧ ¬Board.pivot i j ∈ Board.pathT i j
no goals