Coding this is easy, but coding what you THINK they want is VERY difficult. (1) How can your code run longer than 4 seconds if you had to put a sleep of 3 and a half seconds in the main program part ? (2) If you interrupt it, from the main program, it has already completed, because it only sleeps a second, and the hard coded numSeconds that you pass and have to iterate through takes 3 seconds. So you're never interrupting it.