Method of moments for a uniform on a symmetric interval

Let $x_1=2$, $x_2=1$, $x_3=\sqrt5$, $x_4=\sqrt2$ be the observed values of a random sample of size four from a distribution with the probability density function

$$f(x|\theta)=\begin{cases}\dfrac1{2\theta}, & -\theta\le x\le\theta,\ 0, & \text{otherwise,}\end{cases}\quad\theta>0.$$

Then the method of moments estimate of $\theta$ is