text: #!/usr/bin/env python
  #coding: utf-8
  
  #
  class Solution:
      # @param A, a list of integer
      # @return an integer
      def singleNumber(self, A):
          m = {}
          for a in A:
              m[a] = m.get(a,0) + 1
  
          for a in m:
              if m[a] == 1: return a
  
  
  if __name__ == '__main__':
      s = Solution()
      assert s.singleNumber([2]) == 2
      assert s.singleNumber([2, 3, 3]) == 2
      assert s.singleNumber([4, 4, 2, 3, 3]) == 2
  