let swap : Fin n × Fin n → Fin n × Fin n :=
  fun t => ⟨t.2, t.1⟩
case refine_3
n : Nat
x y : Permutation n
this : ∀ (a b c d : Nat), a + b + (c + d) = a + c + (b + d)
⊢ (BishopFin.count fun a => (↑y[↑a.fst] < ↑y[↑a.snd] ∧ ↑(x * y)[↑a.fst] > ↑(x * y)[↑a.snd]) ∧ ¬↑a.fst < ↑a.snd) =
    BishopFin.count fun t => ↑t.fst < ↑t.snd ∧ ↑y[↑t.fst] > ↑y[↑t.snd] ∧ ↑(x * y)[↑t.fst] < ↑(x * y)[↑t.snd]
case refine_3
n : Nat
x y : Permutation n
this : ∀ (a b c d : Nat), a + b + (c + d) = a + c + (b + d)
swap : Fin n × Fin n → Fin n × Fin n := fun t => (t.snd, t.fst)
⊢ (BishopFin.count fun a => (↑y[↑a.fst] < ↑y[↑a.snd] ∧ ↑(x * y)[↑a.fst] > ↑(x * y)[↑a.snd]) ∧ ¬↑a.fst < ↑a.snd) =
    BishopFin.count fun t => ↑t.fst < ↑t.snd ∧ ↑y[↑t.fst] > ↑y[↑t.snd] ∧ ↑(x * y)[↑t.fst] < ↑(x * y)[↑t.snd]