I have a list…let's say, LKEY

LKEY={1,2,3,4,5}

and then I have a variable, W

How do I check if the the value of W is the same as any element of list LKEY? So that if W is 1, 2, 3, 4, or 5, the check returns as positive.

I've tried a bunch of different commands and can't figure out any algorithms to do this. Simply brute forcing by checking if each individual entry of LKEY is equal to W is insufficient because I need a method that can do the check more quickly than that.

Any ideas?