A buck converter feeding a variable resistive load is shown in the figure. The switching frequency of the switch $S$ is $100$ kHz and the duty ratio is $0.6$. The output voltage $V_{0}$ is $36$ V. Assume that all the components are ideal, and that the output voltage is ripple-free. The value of $R$ (in Ohm) that will make the inductor current ($i_{L}$) just continuous is _________.