def multicharacters(input)
      output = input.gsub(/\([Cc]\)/, "©")
      output = output.gsub(/\([Pp]\)/, "℗")
      output = output.gsub(/\([Rr]\)/, "®")
      output = output.gsub(/\((SM|sm|Sm)\)/, "℠")
      output = output.gsub(/\((TM|tm|Tm)\)/, "™")
      output = output.gsub(/\+-/, "±")
      output = output.gsub(/-\+/, "∓")
      output = output.gsub(/N[oO]\.?\s*(\d+)/, '№\1')
      output = output.gsub(/°C/, '℃')
      output = output.gsub(/°F/, '℉')
    end
def multicharacters(input)
      output = input.gsub(/\([Cc]\)/, "©")
      output = output.gsub(/\([Pp]\)/, "℗")
      output = output.gsub(/\([Rr]\)/, "®")
      output = output.gsub(/\((SM|sm|Sm)\)/, "℠")
      output = output.gsub(/\((TM|tm|Tm)\)/, "™")
      output = output.gsub(/\+-/, "±")
      output = output.gsub(/-\+/, "∓")
      output = output.gsub(/N[oO]\.?\s*(\d+)/, '№\1')
      output = output.gsub(/°C/, '℃')
      output = output.gsub(/°F/, '℉')
    end
Tries to substitute more characters which should be one, like "©", "™", etc.

 @param input [String] The paragraph which will be converted.
 @return [String] Paragraph with converted characters.