Primitive recursive function for $\left[\frac{x}{2}\right] = max\{z ∈ N0 \ | \ 2 · z ≤ x\} $

Question

I need to find a primitive recursive function for

$t(x) = \left[\frac{x}{2}\right] = max\{z \in \ N0 \ | \ 2 · z ≤ x\}$

Unfortunately whatever I come up with isn't primitive recursive. I have also tried "splitting" this but that didn't help me either. A hint in the right direction is highly appreciated!