19.

Birthday boy Julian has holed up in the living room with his headphones and video game and doesn't hear that Grandma and Grandpa are standing at the door. But Grandma doesn't give up so easily and rallies the residents of the high-rise building. Together, they manage to launch a red balloon. The balloon is passed from balcony to balcony, from resident to resident, until it reaches Julian on the 19th floor.