Find the Kth magic number that the only prime factors are 3,5,7

/**
 * FindKthMagicNumber357.java
 * 
 * Description: Design an algorithm to find the kth number such that the
only
 * prime factors are 3, 5, and 7.
 * 
 * @author John Qiao <qiaoshun8888@gmail.com> Date: Jan 26, 2014
 */