The entropy of sorted random variables

Question

If the level of each of $n$ process is represented by $iid$ random variables $x_1,x_2,...,x_n$, which has probability distribution as follows $$ p(x_i) =\frac{x_i}{\sigma^2} exp[ - \frac {x_i^2} {2\sigma^2}] $$ with zero mean and variance $\sigma^2$, let $S$ be a vector of the sorted levels in specific order. How can I find the entropy of $S$.