class BaseClass:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def sumOf(self):
        return self.a + self.b


class ExtendClass(BaseClass):
    def diffOf(self):
        return self.a - self.b


x = BaseClass(10, 9)
s = x.sumOf()
print(s)

y = ExtendClass(12, 4)
sy = y.sumOf()
dy = y.diffOf()
print(sy, dy)