conv =>
  lhs; change bitwise bne n 1
  unfold bitwise; simp [this, hodd]
  change (n/2 ^^^ 0) + (n/2 ^^^ 0)
  rw [Nat.xor_zero, ←Nat.mul_two]
n : Nat
hodd : n % 2 = 1
this : n ≠ 0
⊢ n ^^^ 1 = n - 1
n : Nat
hodd : n % 2 = 1
this : n ≠ 0
⊢ n / 2 * 2 = n - 1