YES(?,POLY) We are left with following problem, upon which TcT provides the certificate YES(?,POLY). Strict Trs: { plus(x, 0()) -> x , plus(x, s(y)) -> s(plus(x, y)) , d(0()) -> 0() , d(s(x)) -> s(s(d(x))) , q(0()) -> 0() , q(s(x)) -> s(plus(q(x), d(x))) } Obligation: innermost runtime complexity Answer: YES(?,POLY) The input was oriented with the instance of 'Polynomial Path Order' as induced by the safe mapping safe(plus) = {1}, safe(0) = {}, safe(s) = {1}, safe(d) = {}, safe(q) = {} and precedence q > plus, q > d, plus ~ d . Following symbols are considered recursive: {plus, d, q} The recursion depth is 2. For your convenience, here are the satisfied ordering constraints: plus(0(); x) > x plus(s(; y); x) > s(; plus(y; x)) d(0();) > 0() d(s(; x);) > s(; s(; d(x;))) q(0();) > 0() q(s(; x);) > s(; plus(d(x;); q(x;))) Hurray, we answered YES(?,POLY)