MAYBE

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           MAYBE
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  ack(0(), y) -> s(y)
     , ack(s(x), 0()) -> ack(x, s(0()))
     , ack(s(x), s(y)) -> ack(x, ack(s(x), y))
     , f(s(x), y) -> f(x, s(x))
     , f(x, s(y)) -> f(y, x)
     , f(x, y) -> ack(x, y)
     , ack(s(x), y) -> f(x, x)}

Proof Output:    
  The input cannot be shown compatible