new_contents: # Ref: https://en.wikipedia.org/wiki/Digital_root
  
  class Solution:
      # @param {integer} num
      # @return {integer}
      def addDigits(self, num):
          if num == 0:
              return 0
          return num - (num - 1) / 9 * 9
  
subject: Create AddDigits_001.py