Louis wants to arrange his CD collection in stack of equal size. He first arranges them in stacks of 2, then stacks of 3 and finally in stacks of 5. He finds that there is always 1 CD left over. What is the least possible number of CDs Louis could have in his collection?
Hint: If there is no CD left, the number of CDs must be a multiple of 2, 3, 5. In other words, 2, 3, and 5 must be factors of the number of CDs.