Please answer the following question: I am a movie director and I just received the following movie plot. Could you help me answer this question? If not, let me know by writing "Not answerable". Plot title: Good Will Hunting Movie plot: This section's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (May 2016) (Learn how and when to remove this template message) Twenty-year-old Will Hunting (Matt Damon) of South Boston is a self-taught, genius-level intellect, though he works as a janitor at the Massachusetts Institute of Technology and spends his free time drinking with his friends, Chuckie (Ben Affleck), Billy (Cole Hauser) and Morgan (Casey Affleck). When Professor Gerald Lambeau (Stellan Skarsgard) posts a difficult mathematics problem as a challenge for his graduate students, Will solves the problem anonymously, stunning both the graduate students and Lambeau himself. As a challenge to the unknown genius, Lambeau posts an even more difficult problem. Lambeau chances upon Will solving the problem but Will flees the scene. That night at a bar, Will meets Skylar (Minnie Driver), a British student about to graduate from Harvard, who plans on attending medical school at Stanford and gives Will her phone number before leaving. The next day as Will and his friends fight a gang at the basketball court, Police arrive and arrest Will. Lambeau visits his court appearance and notices Will's intellect in defending himself. He arranges for him to forgo jail time if he agrees to study mathematics under Lambeau's supervision and participate in therapy sessions. Will tentatively agrees, but treats his first few therapists with contempt and mockery. His refusal to open up is met with staunch defiance by the various therapists, who each refuse to deal with Will further. In desperation, Lambeau calls on Dr. Sean Maguire (Robin Williams), his estranged and much more grounded college roommate, who now teaches psychology at Bunker Hill Community College. Unlike other therapists, Sean actually challenges Will's defense mechanisms, and after a few unproductive sessions, Will begins to open up. Will is particularly struck by Sean's story of how he met his wife by giving up... My question: Who challenges Will's defense mechanisms?
A:
Sean