static <A> int countSubList(L<A> x, L<A> y) {
  int n = 0, lx = l(x), ly = l(y);
  outer: for (int i = 0; i+ly <= lx; i++) {
    for (int j = 0; j < ly; j++)
      if (neq(x.get(i+j), y.get(j)))
        continue outer;
    ++n;
    i += ly-1;
  }
  ret n;
}

static <A> int countSubList(L<A> x, A... y) {
  int n = 0, lx = l(x), ly = l(y);
  outer: for (int i = 0; i+ly <= lx; i++) {
    for (int j = 0; j < ly; j++)
      if (neq(x.get(i+j), y[j]))
        continue outer;
    ++n;
    i += ly-1;
  }
  ret n;
}