MultiSum

PROBLEM STATEMENT

On her first day of math class, Amy was given the following problem:

Find the number of all positive integers not greater than B, that can be
represented as a sum of a positive multiple of X and a positive multiple of Y.
B, X and Y are given positive integer constants.

After reading through it, she immediately formed the system:

0 < T <= B
L1 * X + L2 * Y = T  (of course * takes precedence, by order of operations)

She then asks herself how many integer solutions for T does the system have? 
 
Write a class MultiSum with a method getCount, which takes 3 ints (B, X and Y)
as arguments and returns the number of positive integers that are not greater
than B and are representable as a sum of a positive multiple of X and a
positive multiple of Y.

DEFINITION

Class name:   MultiSum
Method name:  getCount
Parameters:   int, int, int
Returns:      int

Method signature:   (be sure your method is public):
  int getCount(int B, int X, int Y); 

TopCoder will ensure that:
* 1 < X < B
* 1 < Y < B
* 2 < B < 1001

EXAMPLES

Let B = 20, X = 3, Y = 4. The numbers that satisfy our condition are 7, 10,
11, 13, 14, 15, 16, 17, 18, 19, 20. So your method should return 11.

B = 50, X = 7, Y = 13 -> Result = 9
B = 100, X = 10, Y = 10 -> Result = 9
B = 1000, X = 30, Y = 45 -> Result = 61