l3lab/ntp-mathlib huggingface dataset:
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      

Proof state:
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
⊢ Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = Finset.card Finset.univ

Next tactic:
cases n
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · 

Proof state:
case zero
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hn : Nat.zero ≠ 0
c : Fin (Nat.zero + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
⊢ Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = Finset.card Finset.univ

Next tactic:
contradiction
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      

Proof state:
case succ
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
n✝ : ℕ
hn : Nat.succ n✝ ≠ 0
c : Fin (Nat.succ n✝ + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
⊢ Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = Finset.card Finset.univ

Next tactic:
rw [Finset.card_image_iff]
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      

Proof state:
case succ
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
n✝ : ℕ
hn : Nat.succ n✝ ≠ 0
c : Fin (Nat.succ n✝ + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
⊢ Set.InjOn (fun m => c 1 ^ ↑m) ↑Finset.univ

Next tactic:
refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      

Proof state:
case succ
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
n✝ : ℕ
hn : Nat.succ n✝ ≠ 0
c : Fin (Nat.succ n✝ + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
m m' : Fin (i + 1)
h : c 1 ^ ↑m = c 1 ^ ↑m'
⊢ ↑m = ↑m'

Next tactic:
refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by 

Proof state:
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
n✝ : ℕ
hn : Nat.succ n✝ ≠ 0
c : Fin (Nat.succ n✝ + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
m m' : Fin (i + 1)
h : c 1 ^ ↑m = c 1 ^ ↑m'
⊢ 1 ≠ 0

Next tactic:
simp
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      

Proof state:
case succ
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
n✝ : ℕ
hn : Nat.succ n✝ ≠ 0
c : Fin (Nat.succ n✝ + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
m m' : Fin (i + 1)
h : c 1 ^ ↑m = c 1 ^ ↑m'
⊢ c 1 ≠ 0

Next tactic:
exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    

Proof state:
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
⊢ i < n + 1

Next tactic:
suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
    · 

Proof state:
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
H' : ∀ r ∈ Finset.image (fun m => c 1 ^ ↑m) Finset.univ, r ≤ q
⊢ i < n + 1

Next tactic:
simp only [← Nat.succ_le_iff, Nat.succ_eq_add_one, ← this]
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
    · simp only [← Nat.succ_le_iff, Nat.succ_eq_add_one, ← this]
      

Proof state:
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
H' : ∀ r ∈ Finset.image (fun m => c 1 ^ ↑m) Finset.univ, r ≤ q
⊢ Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) ≤ n + 1

Next tactic:
apply card_subset_divisors_le_length_of_chain (@h₂) H'
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
    · simp only [← Nat.succ_le_iff, Nat.succ_eq_add_one, ← this]
      apply card_subset_divisors_le_length_of_chain (@h₂) H'
    

Proof state:
case H'
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
⊢ ∀ r ∈ Finset.image (fun m => c 1 ^ ↑m) Finset.univ, r ≤ q

Next tactic:
simp only [Finset.mem_image]
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
    · simp only [← Nat.succ_le_iff, Nat.succ_eq_add_one, ← this]
      apply card_subset_divisors_le_length_of_chain (@h₂) H'
    simp only [Finset.mem_image]
    

Proof state:
case H'
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
⊢ ∀ (r_1 : Associates M), (∃ a ∈ Finset.univ, c 1 ^ ↑a = r_1) → r_1 ≤ q

Next tactic:
rintro r ⟨a, _, rfl⟩
theorem element_of_chain_eq_pow_second_of_chain {q r : Associates M} {n : ℕ} (hn : n ≠ 0)
    {c : Fin (n + 1) → Associates M} (h₁ : StrictMono c) (h₂ : ∀ {r}, r ≤ q ↔ ∃ i, r = c i)
    (hr : r ∣ q) (hq : q ≠ 0) : ∃ i : Fin (n + 1), r = c 1 ^ (i : ℕ) := by
  classical
    let i := Multiset.card (normalizedFactors r)
    have hi : normalizedFactors r = Multiset.replicate i (c 1) := by
      apply Multiset.eq_replicate_of_mem
      intro b hb
      refine'
        eq_second_of_chain_of_prime_dvd hn h₁ (@fun r' => h₂) (prime_of_normalized_factor b hb) hr
          (dvd_of_mem_normalizedFactors hb)
    have H : r = c 1 ^ i := by
      have := UniqueFactorizationMonoid.normalizedFactors_prod (ne_zero_of_dvd_ne_zero hq hr)
      rw [associated_iff_eq, hi, Multiset.prod_replicate] at this
      rw [this]
    refine' ⟨⟨i, _⟩, H⟩
    have : (Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ)).card = i + 1 := by
      conv_rhs => rw [← Finset.card_fin (i + 1)]
      cases n
      · contradiction
      rw [Finset.card_image_iff]
      refine' Set.injOn_of_injective (fun m m' h => Fin.ext _) _
      refine'
        pow_injective_of_not_unit (element_of_chain_not_isUnit_of_index_ne_zero (by simp) h₁) _ h
      exact Irreducible.ne_zero (second_of_chain_is_irreducible hn h₁ (@h₂) hq)
    suffices H' : ∀ r ∈ Finset.univ.image fun m : Fin (i + 1) => c 1 ^ (m : ℕ), r ≤ q
    · simp only [← Nat.succ_le_iff, Nat.succ_eq_add_one, ← this]
      apply card_subset_divisors_le_length_of_chain (@h₂) H'
    simp only [Finset.mem_image]
    rintro r ⟨a, _, rfl⟩
    

Proof state:
case H'.intro.intro
M : Type u_1
inst✝¹ : CancelCommMonoidWithZero M
inst✝ : UniqueFactorizationMonoid M
q r : Associates M
n : ℕ
hn : n ≠ 0
c : Fin (n + 1) → Associates M
h₁ : StrictMono c
h₂ : ∀ {r : Associates M}, r ≤ q ↔ ∃ i, r = c i
hr : r ∣ q
hq : q ≠ 0
i : ℕ := Multiset.card (normalizedFactors r)
hi : normalizedFactors r = Multiset.replicate i (c 1)
H : r = c 1 ^ i
this : Finset.card (Finset.image (fun m => c 1 ^ ↑m) Finset.univ) = i + 1
a : Fin (Multiset.card (normalizedFactors r) + 1)
left✝ : a ∈ Finset.univ
⊢ c 1 ^ ↑a ≤ q

Next tactic:
refine' dvd_trans _ hr