class Pravokotnik:
    def __init__(self):
        self.stranicaA = 1
        self.stranicaB = 2
        
    @property
    def stranicaA(self):
        return self._a
    @stranicaA.setter
    def stranicaA(self, vr):
        if vr <= 0:
            raise Exception("Napačna vrednost stranice!")
        self._a = vr
        
    @property
    def stranicaB(self):
        return self._b
    @stranicaB.setter
    def stranicaB(self, vr):
        if vr <= 0:
            raise Exception("Napačna vrednost stranice!")
        self._b = vr
        
    def __str__(self):
        return f'{self.stranicaA} x {self.stranicaB}'
    
    @property
    def ploscina(self):
        return self.stranicaA * self.stranicaB
    
    def ploscinaMetoda(self):
        return self.stranicaA * self.stranicaB