I'm trying to simplify this integral
$$ \int_{-\infty}^{-a}e^{-\frac {x^2}{2}} Q(x+a) dx $$
where $ Q(x) = \frac {1}{\sqrt{2\pi}} \int_{x} ^{\infty}\exp(-\frac{v^2}{2})dv $, and $ a>0$
so that the simplified expression will contain only Q-function without integration on it
(I suspect that it can somehow be written as an expression involving $Q^2(\cdot)$)
I would like some help with this.