Instead of hitting In-And-Out Burger after strolling the red carpet of the MTV Movie Awards, Paris Hilton headed off to jail for her first behind-bars meal: cereal, bread and juice. According to Access Hollywood, the heiress checked into the Century Regional Detention Facility in Lynwood just after 11:30 p.m. Sunday, where she's expected to serve three-weeks for violating her probation. Paris opened up about her sentence to the press at the MTV bash. "I am trying to be strong right now," she told reporters on the red carpet. "I'm ready to face my sentence. Even though this is a really hard time, I have my family, my friends and my fans to support me, and that's really helpful." Sheriff's spokesman Steve Whitmore said Paris was a model inmate. "Her demeanor was helpful. She was focused, she was cooperative," he said. It's really happening. Huh.