if the string "Hello" is entered, the following error is generated:

 ValueError: invalid literal for int() with base 10: 'Hello'

At this point we don't have the tools yet to solve this dilemma.
However, it is an interesting to think about it -- a preview of what is coming.
First, one must be able to make a choice so different action can
be taken on different input.  In English we might say:
"If the input is not a number, take some action."
What action might we take?  One option is to write our own error message.
Another option might be to ask again for input with a reminder
that the input should be a number.  We will learn how to take this
action in the next chapter.

A different option is to respond to the error that Python is generating.
That is, we handle the error rather than allowing Python to write its message.  
We could handle the error as we described above.

