How to compute $x^{1/y}$? I'm reading this paper: 
Traceable Ring Signature.

I see this in section 4:

$A_1=(\frac{\sigma_s}{A_0})^{1/s}$

My question is how to compute this, such as: 

$x^{1/y}$

where $x$ is a generator.
$x^{1/y}$ is the $y$th root of $x$, i.e., the element $w$ that satisfies $w^y =x$.

If $x$ generates a group of prime order $q$, it can be shown that this element $w$ is unique and equals $x^z$ where $z$ is the inverse of $y$ modulo $q$. (One way to show this is to use the fact that $x^a = x^b$ if and only if $a \equiv b \pmod q$.)