class Person:
    age=0
    def __init__(self, initialAge):
        if initialAge>0:
            self.age=initialAge
        else:
            self.age=0
            print "Age is not valid, setting age to 0."

    
    def yearPasses(self):
        self.age=self.age+1

    def amIOld(self):
        if self.age<13:
            print "You are young."
        elif self.age>= 13 and self.age<18:
            print "You are a teenager."
        else:
            print "You are old."

class Person:
    age=0
    def __init__(self, initialAge):
        if initialAge>0:
            self.age=initialAge
        else:
            self.age=0
            print "Age is not valid, setting age to 0."

    
    def yearPasses(self):
        self.age=self.age+1

    def amIOld(self):
        if self.age<13:
            print "You are young."
        elif self.age>= 13 and self.age<18:
            print "You are a teenager."
        else:
            print "You are old."
