message: Update missing-number.py
diff: @@ -10,7 +10,7 @@ class Solution(object):
  :type nums: List[int]
  :rtype: int
  """
  - return reduce(operator.xor, nums, \
  + return reduce(operator.xor, nums,
  reduce(operator.xor, xrange(len(nums) + 1)))
  