Pick's Theorem

I recently came across Pick’s theorem, which looks like a neat way to compute the area of a polygon drawn with its edges on a regular grid. The area of the polygon can be expressed using the number of points that lie on the boundaries of the polygon ($n_B$) and the number of points lying inside of the polygon ($n_I$) as follows:

\[Area = \frac{n_B}{2} + n_I - 1\]

Reference: Introduction Proof