static class JNat { }
static class JNatList { }

static class Jzero extends JNat {
  public Jzero() {}
  public boolean equals(Object o) {
    if(o instanceof Jzero) {
      return true;
    }
    return false;
  }
}

static class Jsuc extends JNat {
  public JNat n;
  public Jsuc() { }
  public Jsuc(JNat n) { this.n = n; }
  public boolean equals(Object o) {
    if(o instanceof Jsuc) {
      Jsuc obj = (Jsuc) o;
      return n.equals(obj.n);
    }
    return false;
  }
}