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