As per which Article of the Indian Constitution, the State of Jammu and Kashmir is also a part of Indian Union?

Article 1 states that :
1. India, that is Bharat, shall be a Union of States.
2. The States and the territories there of shall be as specified in the First Schedule.
3. The territory of India shall comprise –
    i. The territories of the States;
    ii. The Union territories specified in the First Schedule; and
    iii. Such other territories as may be acquired.