Top Visitor
A `log` is a site visit log — a list of user ids, each occurrence is one visit. Return the id of the user with the most visits. If several users tie for the lead, return the smallest id among them.
A `log` is a site visit log — a list of user ids, each occurrence is one visit. Return the id of the user with the most visits. If several users tie for the lead, return the smallest id among them.
