static L<S> commonSuffixListCI(L<S> a, L<S> b) {
  int i = 0, nb = l(b), na = l(a), n = min(na, nb);
  while (i < n && eqic(a.get(na-1-i), b.get(nb-1-i)))
    ++i;
  return i == nb ? b : subList(a, na-i);
}