nachos.machine.AssertionFailureError
	at nachos.machine.Lib.assertTrue(Lib.java:77)
	at nachos.userprog.UserKernel.run(UserKernel.java:115)
	at nachos.ag.AutoGrader.run(AutoGrader.java:153)
	at nachos.ag.AutoGrader.start(AutoGrader.java:50)
	at nachos.machine.Machine$1.run(Machine.java:62)
	at nachos.machine.TCB.threadroot(TCB.java:235)
	at nachos.machine.TCB.start(TCB.java:118)
	at nachos.machine.Machine.main(Machine.java:61)