I. Problem Narrative
The purpose of this program is to calculate the prices for a 13% off sale. All prices are to be entered by a user who will enter a -1 after then last price has been entered. The new price is to be calculated by multiplying the old price by 1 - the discount percentage. As soon as the new price is calculated it is output.

II. Interface Analysis
There really should be introductory and exit screens for this program. However, since it is being used as a demo of the priming read, these screens will be skipped.

Inputs:
     All input comes from a user at a keyboard     
     1. Prompt: "Please enter the full price of an item"
         Input:  <price>
 (double)

Outputs: 
     All output goes to the screen
     1. "The discounted price is: <new price>
 (double)