Set: pp::colors
  Set: pp::unicode
  Imported 'macros'
  Imported 'tactic'
  Using: Nat
induct.lean:7:0: error: invalid tactic command, unexpected end of file
Proof state:
a : ℕ, b : ℕ, n : ℕ, iH : a + n = n + a ⊢ a + (n + 1) = n + 1 + a