YES(?,O(n^1)) We are left with following problem, upon which TcT provides the certificate YES(?,O(n^1)). Strict Trs: { norm(nil()) -> 0() , norm(g(x, y)) -> s(norm(x)) , f(x, nil()) -> g(nil(), x) , f(x, g(y, z)) -> g(f(x, y), z) , rem(nil(), y) -> nil() , rem(g(x, y), 0()) -> g(x, y) , rem(g(x, y), s(z)) -> rem(x, z) } 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(norm) = {}, safe(nil) = {}, safe(0) = {}, safe(g) = {1, 2}, safe(s) = {1}, safe(f) = {}, safe(rem) = {1} and precedence norm ~ f, norm ~ rem, f ~ rem . Following symbols are considered recursive: {norm, f, rem} The recursion depth is 1. For your convenience, here are the satisfied ordering constraints: norm(nil();) > 0() norm(g(; x, y);) > s(; norm(x;)) f(x, nil();) > g(; nil(), x) f(x, g(; y, z);) > g(; f(x, y;), z) rem(y; nil()) > nil() rem(0(); g(; x, y)) > g(; x, y) rem(s(; z); g(; x, y)) > rem(z; x) Hurray, we answered YES(?,O(n^1))