PROBLEM STATEMENT
There is a laser cannon at coordinates (0, 0) on the cartesian plane. There are also several 
targets on the plane. Each target is a vertical line segment, and the endpoints of the i-th target 
are at coordinates (x[i], y1[i]) and (x[i], y2[i]). A random angle between -Pi/2 and Pi/2, 
inclusive, is chosen, and a single shot is fired. The angle -Pi/2 is straight down vertically, 0 
is straight to the right horizontally, and Pi/2 is straight up vertically. A shot is a straight 
ray of infinite length starting from the point (0, 0). A shot hits a target if there is a common 
point between them. Return the expected number of targets that will be hit by the single shot. 
Hitting a target doesn't change the direction of the laser shot.

DEFINITION
Class:LaserShooting
Method:numberOfHits
Parameters:vector <int>, vector <int>, vector <int>
Returns:double
Method signature:double numberOfHits(vector <int> x, vector <int> y1, vector <int> y2)


NOTES
-A return value with either an absolute or relative error of less than 1.0e-9 is considered correct.


CONSTRAINTS
-x will contain between 1 and 50 elements, inclusive.
-All elements of x will be distinct.
-x, y1 and y2 will contain the same number of elements.
-Each element of x will be between 1 and 1,000, inclusive.
-Each element of y1 and y2 will be between -1,000 and 1,000, inclusive.
-All targets will have positive lengths.


EXAMPLES

0)
{1}
{-1}
{1}

Returns: 0.5

The only one target will be hit with probability 1/2.

1)
{1,2}
{-1,-2}
{1,2}

Returns: 1.0

Both targets will be hit with probability 1/2.

2)
{3,4,7,1}
{1,2,3,4}
{4,3,2,1}

Returns: 0.4623163952488826



3)
{134,298,151,942}
{-753,-76,19,568}
{440,689,-39,672}

Returns: 1.444210260641501



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