| ∃ a0. a0 ∈ s ∧ ¬ a0 ∈ ∅ ++ a ++ b, b ∈ s, 2 < # s, a ∈ s ⊦ # s = 0, b = a, ∃ a, b, c. a ∈ s ∧ b ∈ s ∧ c ∈ s ∧ a ≠ b ∧ a ≠ c ∧ b ≠ c |
a0 ∈ s, b ∈ s, 2 < # s, a ∈ s ⊦ # s = 0, b = a, a0 = b, a0 = a, ∃ a, b, c. a ∈ s ∧ b ∈ s ∧ c ∈ s ∧ a ≠ b ∧ a ≠ c ∧ b ≠ c
Used simplifier rules: add: ⊦ ¬ a ∈ s ++ b ↔ a ≠ b ∧ ¬ a ∈ s;%in-04: ⊦ a ∈ ∅ ++ b ↔ a = b;