*
* Suppose we have a polynomial @X@ we're trying to reduce mod @P@. If we
* take the topmost nonzero word of @X@, call it @w@, then we can eliminate
*
* Suppose we have a polynomial @X@ we're trying to reduce mod @P@. If we
* take the topmost nonzero word of @X@, call it @w@, then we can eliminate