gas laws - High pressure modification to the van der Waals equation

I get that a gas behaves non-ideally under high pressure and low temperature conditions. At high pressures, the density of a gas increases and attraction forces operate among molecules due to short intermolecular distance. This allows us to somehow modify the ideal gas equation. If a molecule is approaching the wall of container in order to collide, the neighbouring gas molecules soften their impact.

$$p_\text{ideal}=p_\text{real}+\frac{an^2}{V^2}$$

How was the term $\frac{an^2}{V^2}$ derived? My thoughts about that term, $\frac{n^2}{V^2}$ may be the extra pressure thats why the $V$ lies on the numerator (inverse relationship)