Objective: Learn how to implement a "too close" trigger using an ultrasonic sensor connected to an Arduino board.

Overview: The pre-placed code blocks initialize an ultrasonic sensor and use a "while" loop to keep reading the sensor as long as the distance read is greater than 3 inches. Or to put it another way, it keeps reading the sensor until the distance is less than or equal to 3. Then the loop stops and the final distance is displayed. (Note that we insert a half-second delay in the loop so that the sensor doesn't get overloaded with too many readings in too short a time.) After you try running the code, modify it as directed in the Problem Statement.