class Menu:

    def __init__(self, values:list):
        self.values = values
        self.position = 0
    
    def go_up(self):
        self.position = max(0, self.position -1)
    
    def go_down(self):
        self.position = min(len(self.values)-1, self.position +1)
    
    def validate(self):
        return self.values[self.position]