MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { f(x, a(b(y))) -> f(a(a(x)), y) , f(x, b(a(y))) -> f(b(b(x)), y) , f(a(x), y) -> f(x, a(y)) , f(b(x), y) -> f(x, b(y)) } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..