Five face-down cards hold five consecutive integers. On each of five turns you flip a card or guess a hidden card's value, one point per correct guess. What is the best strategy?

A dealer picks five cards carrying five consecutive positive integers and shuffles them face down. You have five turns. On each turn you either flip one card and see its number, or guess the exact number on a card that is still face down. Guesses are only checked after all five turns, and each correct guess scores one point. What is the best strategy and what is its expected score?