def test_11(self): self.assertEqual(next_bigger(11), -1)
def test_1234567890(self): self.assertEqual(next_bigger(59853),83559)
def test_if_only_one(self): self.assertEqual(next_bigger(1), -1)
def test_980(self): self.assertEqual(next_bigger(890), 908)
def test_2016(self): self.assertEqual(next_bigger(2016), 2061)
def test_321(self): self.assertEqual(next_bigger(321), -1)
def test_123(self): self.assertEqual(next_bigger(123), 132)
def test_12(self): self.assertEqual(next_bigger(12), 21)