-3

The tower of happiness is located in the garden of effort.Happiness is waiting for you in the top chamber of the tower.The stairs that lead you to the chamber has N steps and you are allowed to climb up one or two steps from your current location. The door of the chamber will open only if you could climb secrt combination. Of course, finding this secret combination is a matter of chance. For instance, you may choose one of three step stairs: 0 1 2 3,or 0 2 3 or 0 1 3.**sample input:** 3**sample output:** 3