MAYBE

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           MAYBE
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  rev(nil()) -> nil()
     , rev(.(x, y)) -> ++(rev(y), .(x, nil()))
     , car(.(x, y)) -> x
     , cdr(.(x, y)) -> y
     , null(nil()) -> true()
     , null(.(x, y)) -> false()
     , ++(nil(), y) -> y
     , ++(.(x, y), z) -> .(x, ++(y, z))}

Proof Output:    
  The input cannot be shown compatible