Turn Direction of Three Points

Three points $P_1$, $P_2$, $P_3$ on the two dimensional coordinate plane are given. Write a program that decides which way the path from $P_1$ through $P_2$ to $P_3$ turns.

The first line contains the coordinates $x_1$ and $y_1$ of $P_1$, the second line contains $x_2$ and $y_2$ of $P_2$, and the third line contains $x_3$ and $y_3$ of $P_3$, separated by a space.

All coordinates are integers with $-10000 \le x_1, y_1, x_2, y_2, x_3, y_3 \le 10000$. The three points are distinct.

Print $1$ on the first line if the path joining $P_1$, $P_2$, $P_3$ in that order turns counterclockwise, $-1$ if it turns clockwise, and $0$ if the three points lie on one straight line.