Freestyle

In sports like freestyle, excitement often arises from unexpected events rather than physical characteristics alone. Before the Vancouver Olympics, a unique situation caught the attention of journalists: one of the freestyle athletes invented a surprising and skillful new move.

Journalists accredited at the Olympics are eager to write about this story. Already, $M$ out of $N$ journalists know about the athlete's new move. To keep the news interesting each day, one of the following events must occur: either some journalist learns about the story, or some journalist learns that another journalist already knows about the story, or some journalist learns that another journalist does not yet know about the story. If no journalist knows that any other journalist knows about the story, and no journalist knows that any other journalist does not know about the story, what is the maximum number of days the story can keep its interest at the highest level?