old_contents: """Python challenge #10:
  http://www.pythonchallenge.com/pc/return/bull.html"""
  
  
  def main():
      pass
  
  
  if __name__ == "__main__":
      main()
      
new_contents: """Python challenge #10:
  http://www.pythonchallenge.com/pc/return/bull.html"""
  
  
  def main(n=50):
      a = [1, 11, 21, 1211, 111221]
      while len(a) <= 50:
          index = len(a)-1
          temp_a = len(str(a[index-1]))
          temp_b = len(str(a[index]))
          y = temp_a + temp_b
          x = 10**(y-1)
          a.append(x)
      for num, i in enumerate(a):
          print 'num: {}, len: {}'.format(num, len(str(i)))
      return a[50]
  
  
  def prime(x):
      """Return true if prime."""
      for i in xrange(2, x//2):
          if x % i == 0:
              print 'x: {}, i: {}'.format(x, i)
              return False
      return True
  
  if __name__ == "__main__":
      main()
      
subject: Add 10.py, plus prime method.