class Rational:
    
    # constructor method
    def __init__(self,n,d):
        self._numerator = n
        self._denominator = d
        self.reduce()
    
    def reduce(self):
        pass
        
    def add(self,f):
        num = self._numerator * f._denominator + \
              self._denominator * f._numerator
        denom = self._denominator * f._denominator
        return Rational(num,denom)
    
    def __str__(self):
        return str(self._numerator) + "/" + str(self._denominator)
    

r1 = Rational(5,10)
r2 = Rational(2,3)
print(r1)
print(r2)

5/10
2/3

r3 = r1.add(r2)

print(r3)

35/30

str(r3)

'35/30'