require 'set'

fileIn = "FILENAME"
fileOut = "FILENAME"

input = File.new(fileIn, "r")
unique = SortedSet.new()

while (line = input.gets)
  unique << line
end

input.close

output = File.new(fileOut, "w+")

unique.each { |it|
  output.write(it)
}

output.close