Let $f, g : \mathbb{R} \to \mathbb{R}$ be functions defined by $f(x) = \begin{cases} [x], & x < 0 \\ |1 - x|, & x \ge 0 \end{cases}$ and $g(x) = \begin{cases} e^x - x, & x < 0 \\ (x-1)^2 - 1, & x \ge 0 \end{cases}$ where $[x]$ denotes the greatest integer less than or equal to $x$. Then, the function $f \circ g$ is discontinuous at exactly