I don't know how to interpret this strange $\prod$ I have got a $\prod$ that is exactly as follows:

$$\prod\limits_{k=0, k \ne k}^n \frac{x-c_k}{c_k-c_k}$$

I am not sure how to interpret this. My guesses are that it equals either $0, or ,1, or ,x$. But perhaps it isn't defined?

dividing by zero is typically frowned upon and I see a zero in the denominator of each factor, unless there is a typo?
