have h1 : ∀ s, f^[s] a = a := fun s ↦ Function.iterate_fixed fab2 s
f : ℕ+ → ℕ+
hf : ∀ (n : ℕ+), f^[↑(f n)] n * f (f n) = n ^ 2
a b : ℕ+
r : ℕ
fab1 : f^[r] b = a
fab2 : f a = a
⊢ b = a
f : ℕ+ → ℕ+
hf : ∀ (n : ℕ+), f^[↑(f n)] n * f (f n) = n ^ 2
a b : ℕ+
r : ℕ
fab1 : f^[r] b = a
fab2 : f a = a
h1 : ∀ (s : ℕ), f^[s] a = a
⊢ b = a