1603.lean:9:0: error: tactic failed, there are unsolved goals
state:
n : ℕ
⊢ ∃ (v : ℕ),
    v =
      let k : ℕ :=
            (let k : ℕ := (let k : ℕ := (let k : ℕ := (let k : ℕ := n + n in k) + n in k) + n in k) + n in k) +
              n
      in k