exact mem_of_mem_erase (mem_of_mem_erase hk)
α : Type u_1
inst✝¹ : Fintype α
inst✝ : DecidableEq α
i : ℕ
v : α
j : ℕ
M : MultiPart α
hvi : i ∈ range (M.t + 1) ∧ v ∈ MultiPart.P M i
hj : j ∈ range (M.t + 1) ∧ j ≠ i
k : ℕ
hk : k ∈ erase (erase (range (M.t + 1)) j) i
⊢ k ∈ range (M.t + 1)
no goals