∀ a. ¬ a ∈ st ⊦ st = ∅
Used simplifier rules: Dom: ⊦ a ∈ dom st ↔ a ∈ st;% ⊦ ¬ a ∈ ∅; (s)% ⊦ ¬ a ∈ ∅; (s)