def gcd(a, b):
    while b > 0:
        a, b = b, a%b
    return a

class Fraction(object):

    def __init__(self, numerator, denumerator):
        numerator // denumerator # проверка на равенство нулю знаменатель
        cur_gcd = gcd(numerator, denumerator)
        self.numerator = numerator // cur_gcd
        self.denumerator = denumerator // cur_gcd

    def __str__(self):
        if self.denumerator < 0:
            return f'{-self.numerator} / {-self.denumerator}'
        return (f'{self.numerator} / {self.denumerator}')

    def __add__(self, second):
        return Fraction(self.numerator*second.denumerator + self.denumerator * second.numerator,
                       self.denumerator * second.denumerator)

    def __sub__(self, second):
        return Fraction(self.numerator*second.denumerator - self.denumerator * second.numerator,
                       self.denumerator * second.denumerator)