∀ a. ¬ a ∈ st0 ∪ st1 ∧ st1[a] = (∅)[a] ⊦ ¬ a ∈ st0 ∧ ¬ a0 ∈ st1
Used simplifier rules: ⊦ ¬ a ∈ st → st[a] = (∅)[a]; (s)% ⊦ ¬ a ∈ ∅; (s)