Extract the id from a page.

  Args:
    page: a string
  Returns:
    an integer

def get_id(page):
  """Extract the id from a page.

  Args:
    page: a string
  Returns:
    an integer
  """
  start_pos = page.find("<id>")
  end_pos = page.find("</id>")
  assert start_pos != -1
  assert end_pos != -1
  start_pos += len("<id>")
  return int(page[start_pos:end_pos])