apply Exists.elim a1
case h.h.mp
α : Type
inst✝ : DecidableEq α
p q : ℕ
a1 : ∃ stop_state_list, (p = 0 ∧ stop_state_list = [1]) ∧ q ∈ stop_state_list
⊢ p = 0 ∧ q = 1
case h.h.mp
α : Type
inst✝ : DecidableEq α
p q : ℕ
a1 : ∃ stop_state_list, (p = 0 ∧ stop_state_list = [1]) ∧ q ∈ stop_state_list
⊢ ∀ (a : List ℕ), (p = 0 ∧ a = [1]) ∧ q ∈ a → p = 0 ∧ q = 1