a0 ∈ st1, a0 ∈ st0, st0 ⊥ st1 ⊦ a0 = a
Used simplifier rules: ⊦ a ≠ b → (a ∈ st[b, d] ↔ a ∈ st); (s)% ⊦ a ∈ st -- b ↔ a ≠ b ∧ a ∈ st; (s)