#!/usr/bin/env python
#syracuse.py
#a program that runs the syracuse on a number input by the user
# written by ALT 2008

from graphics import *

def syracuse(win, x):
    y = 30
    while x != 1:
        if x % 2 == 0:
            x = x/ 2
            y = y + 1
            blip = Circle(Point(x, y), x/10)
            blip.setOutline('white')
            blip.setFill('white')
            blip.draw(win)
        else:
            x = 3 * x + 1
            y = y + 1
            blip = Circle(Point(x, y), x/10)
            blip.setOutline('white')
            blip.setFill('red')
            blip.draw(win)

def main():
    win = GraphWin("Syracuse", 600, 600)
    win.setBackground('black')
    win.setCoords(0, 0, 100, 100)
    print "A program that runs a number through the Syracuse Sequence.\n"
    x = input("Enter a natural number: ")
    while x != "":
        syracuse(win, x)
        x = input("Enter another natural number: ")

    win.close()

if __name__ == '__main__':
    main()