static class U implements Comparable<U> {
  byte[] data;
  
  *() {}
  *(byte[] *data) {}
  *(S s) { data = toUtf8(s); }
  
  toString { ret fromUtf8(data); }
  
  public int compareTo(U u) {
    ret u == null ? 1 : toString().compareTo(u.toString());
  }
}