| 0 = n - n0, INV(∅, ∅, S1, n0, source), INVR(∅, ∅, S1, n0, n, source, dest) ⊦ |
⊦ INVR(C, N, V, n, n0, source, dest) ↔ ¬ ¬ ( reach(source, dest, n0) ∧ ¬ reach<(source, dest, n0) ∧ n ≤ n0 ∧ ((∃ a. a ∈ C ∧ reachS(a, {dest} , n0 - n)) ∨ n < n0 ∧ (∃ b. b ∈ N ∧ reachS(b, {dest} , n0 - n - 1))))
[[CONCRETESIMPRULES : ([CSIMPSEQ : ⊦ m ≤ n → (n - m = 0 ↔ n = m)], [CSIMPSEQ : ⊦ ¬ a ∈ ∅])], [EXTRATERMS : (dest, source, n, n0, S1, ∅, ∅)]]