A guy gets a flat tire in front of a mental hospital.
As he's putting on the spare, the four nuts for securing the tire to the car accidentally fall down a storm grate.
He's distraught because he doesn't know what to do.
A mental patient watching the whole episode from behind a fence says: "Why don't you just take one nut off each of the other three tires and put the spare on with those? That should hold you until you get to a service station."
The man is amazed. What a great idea!
Then he says, "But you're a mental patient. How'd you think of something so clever?"
The patient says, "I may be crazy, not I'm not stupid."
Just so you know.