$$f(x)=\{\begin{array}{cc}\hfill 1/3\hfill & \text{if\ }0\≤x\≤1;\hfill \\ \hfill 2/3\hfill & \hfill \text{if\ }3\≤x\≤4;\hfill \\ \hfill 0\hfill & \text{elsewhere.}\hfill \end{array}$$