MAYBE

'Pop* with parameter subtitution (timeout of 60.0 seconds)'
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Answer:           MAYBE
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  app(nil(), xs) -> nil()
     , app(cons(x, xs), ys) -> cons(x, app(xs, ys))
     , rev(nil()) -> nil()
     , rev(cons(x, xs)) -> append(xs, rev(cons(x, nil())))
     , shuffle(nil()) -> nil()
     , shuffle(cons(x, xs)) -> cons(x, shuffle(rev(xs)))}

Proof Output:    
  The input cannot be shown compatible