MAYBE

We are left with following problem, upon which TcT provides the
certificate MAYBE.

Strict Trs:
  { isEmpty(cons(x, xs)) -> false()
  , isEmpty(nil()) -> true()
  , isZero(0()) -> true()
  , isZero(s(x)) -> false()
  , head(cons(x, xs)) -> x
  , tail(cons(x, xs)) -> xs
  , tail(nil()) -> nil()
  , p(0()) -> 0()
  , p(s(0())) -> 0()
  , p(s(s(x))) -> s(p(s(x)))
  , inc(0()) -> s(0())
  , inc(s(x)) -> s(inc(x))
  , sumList(xs, y) ->
    if(isEmpty(xs),
       isZero(head(xs)),
       y,
       tail(xs),
       cons(p(head(xs)), tail(xs)),
       inc(y))
  , if(false(), false(), y, xs, ys, x) -> sumList(ys, x)
  , if(false(), true(), y, xs, ys, x) -> sumList(xs, y)
  , if(true(), b, y, xs, ys, x) -> y
  , sum(xs) -> sumList(xs, 0()) }
Obligation:
  innermost runtime complexity
Answer:
  MAYBE

The input cannot be shown compatible

Arrrr..