a ∈ st ⊦ ∃ a, d, st0. st = st0[a, d] ∧ ¬ a ∈ st0, ¬ a ∈ st ∧ st[a] = (∅)[a]
Used simplifier rules: notmemlookup: ⊦ ¬ a ∈ st → st[a] = (∅)[a]; Used formulas: a ∈ st