Deal or no deal?
Raj, an artifacts dealer, has to sell artifacts to the other corner of the city. He has three bags, with each bag containing 30 artifacts which totals to 90 artifacts. He is carrying all the three bags with him.
Now in his way are 30 checkpoints. Each checkpoint being a few kilometers away from each other. He has to pass through all 30 checkpoints. While crossing through a checkpoint he will have to give one artifact from each bag, otherwise he will not be allowed to pass through the checkpoint.
There is no other way except the way in which the 30 checkpoint exist.
After passing through all the checkpoints, how many artifacts is he left with?
Stipulation and Assumptions: If required the bags can be disposed off. Transfer of artifacts from one bag to another is allowed. No other ways are possible to save the artifacts.