Input/Output Example with Input Validation

This is identical to example #4 from this lesson, but this one validates the user input.
That means if you enter bad input, the script will ask you to re-enter input that is valid.

The input is an exam score so it must be between 0 and 100, inclusive.
But it must also be a number, meaning the user can't enter something inherently non-numeric, like a word.
Forcing the input to be a number will mitigate the potential for "garbage in ... garbage out."
Enter a word in the previous overtime pay example, and you will see ample evidence of garbage output.