automatic terminate after 5 invalid entries

I am doing an assignment which I have to write a program using a do statement that prompts for a grade between 0 and 100, then displays the grade, alerts when an invalid grade is entered, exit the program when 999 is entered and terminates after 5 invalid grades have been entered. I have done all the assignment except I cant find my way around the terminates after 5 invalid entries. Can anyone point me in the right direction?? Thanks

errmmm very very difficult..... *thinks for an hour or two*

Use a variable for invalid reads incrementing it after every bad read and check it for 5 invalid reads. If so use exit(0) to end the program.