calc
  LenBit (2 * j * i) (a * (2 * j) + r + j) ↔ LenBit (i * (2 * j)) (a * (2 * j) + (r + j)) := by
    simp [mul_comm (2 * j), add_assoc]
  _                                        ↔ LenBit i a                                   :=
    lenbit_mul_add pi' (by simpa using pj') (by simp [two_mul, hr])
  _                                        ↔ LenBit (i * (2 * j)) (a * (2 * j) + r)       :=
    Iff.symm <| lenbit_mul_add pi' (by simpa using pj') (lt_of_lt_of_le hr $ by simp)
  _                                        ↔ LenBit (2 * j * i) (a * (2 * j) + r)         := by
    simp [mul_comm]
case inr.inr.intro.intro.intro.intro
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈𝚫₀
j : M
pj : Pow2 j
i : M
hij : 2 * j * i > j
a r : M
hr : r < j
h : ¬LenBit j (a * (2 * j) + r)
pi : Pow2 j ∧ Pow2 i
pi' : Pow2 i
pj' : Pow2 j
⊢ LenBit (2 * j * i) (a * (2 * j) + r + j) ↔ LenBit (2 * j * i) (a * (2 * j) + r)
no goals