6.4 How do I fix the program?

You need to figure out what the program is doing. You need to figure out what the program should do. Figure out what the difference between the two is. Debugging is a skill that has to be done to be learned. If you can't figure it out after an hour or so take a break, talk to someone about the problem or contemplate the lint in your navel. Come back in a while and you will probably have new ideas about the problem. Good luck.