You are shown five cards lying on a table (so you can only see one side of each of the five cards). Each card has a single positive integer printed on each side of the card (they may or may not be repeated). The numbers that you can see are: 1, 2, 3, 4, and 5. How many cards must you turn over to completely verify the statement any card that has a 2 on one side has a 5 on the opposite side ?