Let f\left( x \right) = \,\left\{ {\begin{array}{*{20}{c}} {\max \left\{ {\left| x \right|,{x^2}} \right\},}{\left| x \right| \leqslant 2} \\ {8 - 2\left| x \right|,}{2 < \left| x \right| \leqslant 4} \end{array}} \right. Let S be the set of points in the interval (–4,4)

at which f is not differentiable. Then S: