Birbal is a witty trader who trade of a mystical fruit grown far in north.

He travels from one place to another with three sacks which can hold 30 fruits each.

None of the sack can hold more than 30 fruits. On his way, he has to pass through thirty check points and at each check point, he has to give one fruit for each sack to the authorities.

How many mystical fruits remain after he goes through all the thirty check points?