@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		PII other = (PII) obj;
		if (a != other.a)
			return false;
		if (b != other.b)
			return false;
		return true;
	}