Four point charges, each of $+q$, are rigidly fixed at the four corners of a square planar soap film of side ' $a$ '. The surface tension of the soap film is $\gamma$. The system of charges and planar film are in equilibrium, and $\mathrm{a}=\mathrm{k}\left[\frac{\mathrm{q}^2}{\gamma}\right]^{1 / \mathrm{N}}$, where ' k ' is a constant. Then N is