35. In $\triangle A B C$, $\angle A C B=90^{\circ}, \angle A=31^{\circ}$, with $C$ as the center, $\triangle A B C$ is rotated by an angle $\theta$ to $\triangle A_{1} B_{1} C$ (the shape and size of $\triangle A B C$ remain unchanged during the rotation), and point $B$ exactly falls on $A_{1} B_{1}$. Then the size of the rotation angle $\theta$ is $\qquad$ ${ }^{\circ}$.
Answer: 62