Roots and Arctangents

Let $x_1, x_2, x_3$ be the roots of $x^3 - 17x - 18 = 0$, with $-4 < x_1 < -3$ and $4 < x_3 < 5$.

1. Find the integer part of $x_2$. 2. Evaluate $\arctan x_1 + \arctan x_2 + \arctan x_3$.