k transparent slabs are arranged one over another.

$k$ transparent slabs are arranged one over another. The refractive index of the slabs are $\mu_{1}, \mu_{2}, \mu_{3}, \ldots \ldots \ldots \ldots \ldots \mu_{\mathrm{k}}$ and the thickness are $t_{1}, t_{2}, t_{3} \ldots \ldots \ldots \ldots t_{k}$. An object is seen through this combination with nearly perpendicular light. Find the equivalent refractive index of the system which will allow the image to be formed at the same place.