YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { f(X) -> n__f(X) , f(0()) -> cons(0(), n__f(n__s(n__0()))) , f(s(0())) -> f(p(s(0()))) , 0() -> n__0() , s(X) -> n__s(X) , p(s(0())) -> 0() , activate(X) -> X , activate(n__f(X)) -> f(activate(X)) , activate(n__s(X)) -> s(activate(X)) , activate(n__0()) -> 0() } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) Arguments of following rules are not normal-forms: { f(0()) -> cons(0(), n__f(n__s(n__0()))) , f(s(0())) -> f(p(s(0()))) , p(s(0())) -> 0() } All above mentioned rules can be savely removed. We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { f(X) -> n__f(X) , 0() -> n__0() , s(X) -> n__s(X) , activate(X) -> X , activate(n__f(X)) -> f(activate(X)) , activate(n__s(X)) -> s(activate(X)) , activate(n__0()) -> 0() } Obligation: innermost runtime complexity Answer: YES(?,O(n^1)) The input was oriented with the instance of 'Small Polynomial Path Order (PS,1-bounded)' as induced by the safe mapping safe(f) = {1}, safe(0) = {}, safe(cons) = {1, 2}, safe(n__f) = {1}, safe(n__s) = {1}, safe(n__0) = {}, safe(s) = {1}, safe(p) = {}, safe(activate) = {} and precedence activate > f, activate > 0, activate > s, f ~ 0, f ~ s, 0 ~ s . Following symbols are considered recursive: {activate} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: f(; X) > n__f(; X) 0() > n__0() s(; X) > n__s(; X) activate(X;) > X activate(n__f(; X);) > f(; activate(X;)) activate(n__s(; X);) > s(; activate(X;)) activate(n__0();) > 0() Hurray, we answered YES(?,O(n^1))