TIMEOUT We are left with following problem, upon which TcT provides the certificate TIMEOUT. Strict Trs: { qsort(nil()) -> nil() , qsort(cons(x, xs)) -> append(qsort(filterlow(last(cons(x, xs)), cons(x, xs))), cons(last(cons(x, xs)), qsort(filterhigh(last(cons(x, xs)), cons(x, xs))))) , append(nil(), ys()) -> ys() , append(cons(x, xs), ys()) -> cons(x, append(xs, ys())) , filterlow(n, nil()) -> nil() , filterlow(n, cons(x, xs)) -> if1(ge(n, x), n, x, xs) , last(nil()) -> 0() , last(cons(x, nil())) -> x , last(cons(x, cons(y, xs))) -> last(cons(y, xs)) , filterhigh(n, nil()) -> nil() , filterhigh(n, cons(x, xs)) -> if2(ge(x, n), n, x, xs) , if1(true(), n, x, xs) -> filterlow(n, xs) , if1(false(), n, x, xs) -> cons(x, filterlow(n, xs)) , ge(x, 0()) -> true() , ge(0(), s(x)) -> false() , ge(s(x), s(y)) -> ge(x, y) , if2(true(), n, x, xs) -> filterhigh(n, xs) , if2(false(), n, x, xs) -> cons(x, filterhigh(n, xs)) } Obligation: innermost runtime complexity Answer: TIMEOUT Computation stopped due to timeout after 60.0 seconds. Arrrr..