⊦ ∃ n. n < # y + 1 + # z ∧ (y + a ' + z)[n] = a
Used simplifier rules: ⊦ # a ' = 0 +1; (s)% ⊦ #(x + y) = # x + # y; (s)%a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a + x = a ' + x; (s)