simp [under, show exp a - 1 + 1 = exp a from sub_add_self_of_le (by simp)]
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈𝚺₁
a : M
⊢ a < under a + 1
no goals