■

require 'net/http'

Net::HTTP.version_1_2   
text = 
  /-->/.match(
    /<!--/.match(
      /<!--/.match(
        Net::HTTP.start('www.pythonchallenge.com', 80) {|http|
	  response = http.get('/pc/def/ocr.html')
          response.body
        }
      ).post_match		
    ).post_match
  ).pre_match


def text.uniq
  uniq_keys = 
  self.split(//).inject(Hash.new(0)){|h,c| 
    h[c] += 1; h
  }.to_a.select{|key, count| 
    count == 1
  }.collect{|key,count| 
    key
  }.join
  
  self.split(//).select{|node| 
    uniq_keys.include?(node)
  }.join
end

p text.uniq