| #(s0 ++ a0) < 2, b ∈ s0 ++ a0, a ∈ s0 ++ a0, ∀ a, b. # s0 < 2 ∧ a ∈ s0 ∧ b ∈ s0 → a = b ⊦ a = b |
#(s0 ++ a0) < 2, ∀ a, b. # s0 < 2 ∧ a ∈ s0 ∧ b ∈ s0 → a = b, a = a0 ∨ a ∈ s0, b = a0 ∨ b ∈ s0 ⊦ a = b
Used simplifier rules: In-insert: ⊦ a ∈ s ++ b ↔ a = b ∨ a ∈ s;