import java.util.LinkedList;
import java.util.Queue;

public class Queue@R_304_2187@ {

  PRivate Queue<Integer> queue;


  private int size ;//滑动窗口的size

    int sum = 0;

    public static void main(String[] args) {

        Queuetest queuetest = new Queuetest(3);
        System.out.println(queuetest.next(1));
        System.out.println(queuetest.next(3));
        System.out.println(queuetest.next(2));
        System.out.println(queuetest.next(4));
        System.out.println(queuetest.next(6));
        System.out.println(queuetest.next(2));
    }


  public Queuetest(int size){
        this.size = size;
        queue = new LinkedList<Integer>();
    }

    public double next(int val){
        if(size == queue.size()) {
            Integer poll = queue.poll();
            sum -= poll;
            queue.add(val);
            return (sum+=val)/size;
        }
        else
        {
            queue.add(val);
            return (sum+=val)/queue.size();
        }

    }


}