36. Given that each of the values of $x_{1}, x_{2}, \cdots \cdots, x_{2018}$ is either -1 or 1, if $x_{1}+x_{2}+\cdots+x_{2018}=4$, then the maximum value of $\left|x_{1}-x_{2}\right|+\left|x_{3}-x_{4}\right|+\cdots+\left|x_{2017}-x_{2018}\right|$ is $\qquad$
answer: 2014