Mean of a variable from a factorising joint density

Let $X$ and $Y$ be continuous random variables with the joint probability density function

$$f(x,y)=\begin{cases}c\,\dfrac{x^2}{y^3}, & 0<x<1, y>1,\ 0, & \text{otherwise,}\end{cases}$$

where $c$ is a suitable constant. Then $E(X)=$ ________________________