import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.Deque;
import java.util.ArrayDeque;
// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) {
        Deque<Integer> deq=new ArrayDeque<>();
        deq.offerFirst(10);
        deq.addFirst(20);
        deq.offerFirst(30);
        deq.addFirst(40);
        deq.addFirst(50);
        for(int val:deq)
            {
                System.out.println(val);
            }
        System.out.println(deq.getFirst()+" "+deq.getLast());
        System.out.println(deq.peekFirst()+" "+deq.peekLast());
        deq.removeFirst();
        deq.removeLast();
        for(int val:deq)
            {
                System.out.println(val);
            }
        deq.pollFirst();
        deq.pollLast();
        for(int val:deq)
            {
                System.out.println(val);
            }
        
    }
}