Unique Paths 

/**
	 * A robot is located at the top-left corner of a m x n grid (marked
'Start'
	 * in the diagram below).
	 * 
	 * The robot can only move either down or right at any point in time.
The
	 * robot is trying to reach the bottom-right corner of the grid (marked
	 * 'Finish' in the diagram below).
	 * 
	 * How many possible unique paths are there?
	 * 
	 * XXXXXX XXXXXX XXXXXX XXXXXX
	 * XXXXXX XXXXXX XXXXXX XXXXXX
	 * XXXXXX IMAGE HERE :P XXXXXX
	 * XXXXXX XXXXXX XXXXXX XXXXXX
	 * XXXXXX XXXXXX XXXXXX XXXXXX
	 * 
	 * Above is a 3 x 7 grid. How many possible unique paths are there?
	 * 
	 * Note: m and n will be at most 100.
	 * 
	 * */