val my_urls = """urbanc""".r

def crawl(url: String, n: Int) : Unit = {
  if (n == 0) ()
  else if (my_urls.findFirstIn(url) == None) ()
  else {
    println("Visiting: " + n + " " + url)
    for (u <- get_all_URLs(get_page(url))) crawl(u, n - 1)
  }
}