Read the problem statement carefully. Its a very realistic,practical and easy problem. Draw a picture to help yourself for finding the solution. Keep in mind that the worm will move leftwards or rightwards from its initial position according to input of starting volume and ending volume. It is also possible that the worm started and ended in the same volume...
Happy Coding...:)

First i did not understand this problem.but your suggestions help me.thanks!!!And it is really very practical, realistic and easy problem!!