Let \( f: \mathbb{R} \to \mathbb{R} \) be defined by
\[ f(x) = \begin{cases} a - \frac{\sin[x-1]}{x-1} & , \text{if } x>1 \\ 1 & , \text{if } x = 1 \\ b - \frac{\sin([x-1] - [x-1]^3)}{([x-1]^2)} & , \text{if } x<1 \end{cases} \]
where \([t]\) denotes the greatest integer less than or equal to t. If f is continuous at \(x=1\), then \(a+b=\)