class Polynomial:
    def __init__(self, coefficients):
        self.coeff = coefficients

    def __call__(self, x):
        """Evaluate the polynomial."""
        s=0
        for i in range(len(self.coeff)):
            s += self.coeff[i]*x**i
        return s

    def __add__(self, other):
        """Return self + other as Polynomial object."""

        if len(self.coeff) > len(other.coeff):
            result_coeff = self.coeff[:]  # copy!
            for i in range(len(other.coeff)):
                result_coeff[i] += other.coeff[i]
        else:
            result_coeff = other.coeff[:] # copy!
            for i in range(len(self.coeff)):
                result_coeff[i] += self.coeff[i]
        return Polynomial(result_coeff)

    def __sub__(self, other):
        neg_coeff = [-coeff for coeff in other.coeff]
        neg_p = Polynomial(neg_coeff)
        return self + neg_p

def test_Polynomial():

    p1 = Polynomial([1, 2, 1])
    p2 = Polynomial([2, 2, 3])
    p3 = p1 - p2

    assert p3.coeff == [-1, 0, -2]
    

    p1 = Polynomial([1, 2, 1])
    p2 = Polynomial([2, 2])
    p3 = p1 - p2

    assert p3.coeff == [-1, 0, 1]


    p1 = Polynomial([1, 2])
    p2 = Polynomial([2, 2, 3])
    p3 = p1 - p2

    assert p3.coeff == [-1, 0, -3]


test_Polynomial()
print("Everything is good")