*   event-controlled loop

    *   repeat until some "event" occurs, making the
        while's condition false

    *   example: ask the user for a ticket price, and
        determine how many performances it would take
        to get to 500 attendees at that ticket price

    *   contract: event1: void -> void

def event1():

        purpose: is to ask the user for a ticket price, and
        determine and print to the screen how many performances 
        it would take to get to 500 attendees at that ticket price

        example: if when you run event1() you enter a
                 ticket price of 5, then the following 
                 should be printed to the screen:

It will take 5 performances to get to at least 500 attendees

    # get desired ticket price from user

    # initialize needed variables
    # num_performances, total_attendees

    # find out how many attendees per performance at
    #    this ticket price

    # while total_attendees < 500

         increase num_performances

         add 1-performance attendees to total_attendees

    # print out the final num_performances