A basket contains a number of eggs. The first buyer bought $1/2$ of the contents of the basket with one free. Then the second buyer bought also one-half of the contents of the remaining and got one free. The same for the customer who bought $1/2$ of the contents with one free, until the fourth and last buyer who bought the half of the remaining with one free and nothing left. How many eggs were in the basket?

This is not my original :D