MAYBE

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

Strict Trs:
  { leq(0(), x) -> tt()
  , leq(s(x), 0()) -> ff()
  , leq(s(x), s(y)) -> leq(x, y)
  , split(nil()) -> app(nil(), nil())
  , split(cons(x, nil())) -> app(cons(x, nil()), nil())
  , split(cons(x, cons(y, xs))) -> split1(x, y, split(xs))
  , split1(x, y, app(xs, ys)) -> app(cons(x, xs), cons(y, ys))
  , merge(xs, []()) -> xs
  , merge(cons(x, xs), cons(y, ys)) ->
    ifmerge(leq(x, y), x, y, xs, ys)
  , merge([](), xs) -> xs
  , ifmerge(tt(), x, y, xs, ys) -> cons(x, merge(xs, cons(y, ys)))
  , ifmerge(ff(), x, y, xs, ys) -> cons(y, merge(cons(x, xs), ys))
  , mergesort(xs) -> mergesort1(split(xs))
  , mergesort1(app(xs, ys)) -> merge(mergesort(xs), mergesort(ys)) }
Obligation:
  innermost runtime complexity
Answer:
  MAYBE

The input cannot be shown compatible

Arrrr..