The horizontal flat surface rolling two balls of radius R meters each. At the initial time balls are the coordinates of points (x_1, y_1) and (x_2, y_2) and the velocity projections on the coordinate axes dx_1 dy_{1 }and dx_2 dy_2 meters per second, respectively.
Required to find the time in seconds, after which balls faced, or determine that it will not happen.
The input file contains the real numbers R x_1 y_1 dx_1 dy_1 x_2 y_2 dx_2 dy_2.
Output file must contain a real number - the time before the collision, accurate to 3 significant digits after the decimal point, or −1, if no collision occurs.
1 ≤ R ≤ 1000, -1000 ≤ x_1, y_1, dx_1, dy_1, x_2, y_2, dx_2, dy_2 ≤ 1000