def p40(positions: List[int]) -> int: return prod(champernowne_digit(n) for n in positions)
def test_1000000(self): self.assertEqual(champernowne_digit(1000000), 1)
def test_15(self): self.assertEqual(champernowne_digit(15), 2)
def test_12(self): self.assertEqual(champernowne_digit(12), 1)
def test_5(self): self.assertEqual(champernowne_digit(5), 5)
def test_0(self): self.assertEqual(champernowne_digit(0), 0)