Q52

Consider a Boolean function $f(w,x,y,z)$ such that

$$\begin{array}{lll} f(w,0,0,z) & = & 1 \\ f(1,x,1,z) & =& x+z \\ f(w,1,y,z) & = & wz +y \end{array}$$

The number of literals in the minimal sum-of-products expression of $f$ is _________