YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { a(b(x)) -> b(a(x)) , a(c(x)) -> x } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) The input was oriented with the instance of 'Small Polynomial Path Order (PS)' as induced by the safe mapping safe(a) = {}, safe(b) = {1}, safe(c) = {1} and precedence empty . Following symbols are considered recursive: {a} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: a(b(; x);) > b(; a(x;)) a(c(; x);) > x Hurray, we answered YES(?,O(n^1))