Find $ \#\left\{ (x,y)\in\mathbb{N}^2\bigg| \frac{1}{\sqrt{x}} -\frac{1}{\sqrt{y}} =\frac{1}{2016}\right\} $, where $ \# A $ is the cardinality of $ A $.

Let's think step by step and output the final answer within \boxed{}.
user