CONO-SUR 2009 Problem 6

Sebastian has a certain number of rectangles with areas that sum up to 3 and with side lengths all less than or equal to $1$ . Demonstrate that with each of these rectangles it is possible to cover a square with side $1$ in such a way that the sides of the rectangles are parallel to the sides of the square.Note: The rectangles can overlap and they can protrude over the sides of the square.