I want to convert a binary code to a grey code using 16-to-1 MUX

The problem is that I didn't learned yet adders or VHDL (which a lot of people are telling me to use them) but all I have is 16-to-1 MUXs.

Should I link each MUX with the other from the select input? (Knowing that I have 4 inputs and 4 outputs obviously)

P.S: I am new to this kind of stuff and I am having a hard time to solve this.

Thank you in advance.