The equation of a circle is $\text{Re}(z^2) + 2(\text{Im}(z))^2 + 2\text{Re}(z) = 0$, where $z = x + iy$. A line which passes through the centre of the given circle and the vertex of the parabola $x^2 = 6x - y + 13 = 0$ has $y$-intercept equal to: