If $\sin^{-1}\!\left(\dfrac{\alpha}{17}\right)+\cos^{-1}\!\left(\dfrac{4}{5}\right)-\tan^{-1}\!\left(\dfrac{77}{36}\right)=0,\ 0<\alpha<13$, then $\sin^{-1}(\sin\alpha)+\cos^{-1}(\cos\alpha)$ is equal to: