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//Type Definition
trait IntQueue {
  def get(): Int
  def put(x: Int)
  def size(): Int
}

//ArrayBuffer implementation
class IntQueueImpl extends IntQueue {
  private[this] val buf = new collection.mutable.ArrayBuffer[Int]
  def get = buf remove 0
  def put(x: Int) { buf += x }
  def size = buf.length
}

trait Doubling extends IntQueue {
  abstract override def put(x: Int) { super.put(2 * x) }
}

trait Incrementing extends IntQueue {
  abstract override def put(x: Int) { super.put(x + 1) }
}

trait Filtering extends IntQueue {
  abstract override def put(x: Int) { if (x > 0) super.put(x) }
}