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)