Moment of the minimum of exponentials

Let $X_1, X_2$ and $X_3$ be three independent random variables such that $X_k$ ($k = 1, 2, 3$) has the following probability density function $f_k(x) = \begin{cases} k e^{-kx}, & x > 0 \ 0, & \text{otherwise} \end{cases}$. Let $Y = \min\{X_1, X_2, X_3\}$. Then the value of $E(3Y^2 - Y)$ equals ________ (answer in integer).