class Rational:
    def __init__(self, n, d):
        if n == 0:
            self.nom = 0
            self. denom = 1
        else:
            nod = NOD(n,d)
            self.nom = n // nod
            self.denom = d // nod

    def __str__(self):
        return str(self.nom) + '/' + str(self.denom)