If the president has vetoed a bill passed by congress, what can congress do about it?

The Congress can override a veto by passing the act by a two-thirds vote in both the House of Representatives  and the Senate.

According to the Constitution. All legislation passed by both houses of Congress must be presented to the President. ... If the Congress overrides the veto by a two-thirds vote in each house, it becomes law without the President's signature.

because the earth is a round globe. but that is just what they tell us it is flat and those dudes actually where lying they sailed east.