Who discharges the functions of the President when there are vacancies in the offices of both the President and the Vice-President?

 While exercising its powers under Article 70 of the Constitution, the Parliament enacted the President (Discharge of Functions) Act in 1969 for this contingency. 

 This Act provides as under: 

 In the event of the occurrence of vacancies in the offices of both the President and the Vice-President, the Chief Justice of India or, in his absence, the seniormost Judge of the Supreme Court available shall discharge the functions of the President until a new President enters upon his office or a new VicePresident begins to act as President under article 65, whichever is earlier.