Today, her friend Annie called her to get two rosettes which were missing at the regional cat show. "Never mind the choice of colour", Annie said, "but both rosettes must be of the same colour!"

Bad luck, it was very late on the show eve when Annie called, and there was a power shortage in the area. Valérie was unable to see the colour of the rosettes when she took them out of her drawer.

How many rosettes must she take out to be sure that at least two of them are of the same colour ?