∀ m. m < n0 → n0 = 0 ∨ (∃ m0. m + m0 = n0 ∧ m0 ≠ 0), m < n0 +1 ⊦ n0 +1 = 0, ∃ m0. m + m0 = n0 +1 ∧ m0 ≠ 0
Used simplifier rules: nat freely generated by 0, +1;;