ext a
t : ℕ
P : ℕ → ℕ
h : Balanced t P
this : ∀ (i : ℕ), i ∈ range (t + 1) → P i = minP t P ∨ P i = minP t P + 1
⊢ range (t + 1) = smallParts h ∪ largeParts h
case a
t : ℕ
P : ℕ → ℕ
h : Balanced t P
this : ∀ (i : ℕ), i ∈ range (t + 1) → P i = minP t P ∨ P i = minP t P + 1
a : ℕ
⊢ a ∈ range (t + 1) ↔ a ∈ smallParts h ∪ largeParts h