Moment of inertia of a disc of mass '$M$' and radius '$R$' about any of its diameter is $\frac{M R^{2}}{4}$. The moment of inertia of this disc about an axis normal to the disc and passing through a point on its edge will be, $\frac{x}{2}$ MR$^{2}$. The value of $x$ is ___________.