Congress can override the president’s veto with a two-thirds majority.
Explanation:
The Constitution of the United States is designed in such a manner that it together allows the Senate and the House of Representatives to override the President's decision of vetoing a decision made by the Congress.
For the Congress to be able to exercise this power of overriding the President's veto, it is necessary for it to secure a special majority in both the Senate and the House of Representatives by two-thirds of senators and congressmen voting against President's veto.