Problem:
Doubly Linked List

Your task is to implement a double linked list.

Write a program which performs the following operations:

insert x: insert an element with key x into the front of the list.

delete x: delete the first element which has the key of x from the list. If there is not such element, you need not do anything.

deleteFirst: delete the first element from the list.

deleteLast: delete the last element from the list.

Input

The input is given in the following format:

n

command1

command2

...

commandn

In the first line, the number of operations n is given. In the following n lines, the above mentioned operations are given in the following format:

insert x

delete x

deleteFirst

deleteLast

Output

Print all the element (key) in the list after the given operations. Two consequtive keys should be separated by a single space.

Constraints

The number of operations ≤ 2,000,000

The number of delete operations ≤ 20

0 ≤ value of a key ≤ 109

The number of elements in the list does not exceed 106

For a delete, deleteFirst or deleteLast operation, there is at least one element in the list.

Sample Input 1

7
insert 5
insert 2
insert 3
insert 1
delete 3
insert 6
delete 5

Sample Output 1

6 1 2

Sample Input 2

9
insert 5
insert 2
insert 3
insert 1
delete 3
insert 6
delete 5
deleteFirst
deleteLast

Sample Output 2

1

Solution in JAVA (judge verdict: Wrong Answer)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.util.Scanner;
import java.util.ArrayDeque;
import java.util.Deque;

public class Main {
    public static void main(String[] args) throws IOException{
        // Prints "Hello, World" to the terminal window.
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    	int n = Integer.parseInt(br.readLine());
    	int i = 0;
    	String orders[] = new String[n];
    	Deque<String> doubly_linked_list = new ArrayDeque<String>();
    	StringBuilder ans = new StringBuilder();
    	
    	while(i++ < n){
    		String[] order_word = br.readLine().split(" ");
    		String order = order_word[0];
    		String num = order_word[0];
    		
    		if(order.equals("insert")){
    			doubly_linked_list.addFirst(num);
    		}
    		if(order.equals("delete")){
    			doubly_linked_list.remove(num);
    		}
    		if(order.equals("deleteFirst")){
    			doubly_linked_list.removeFirst();
    		}
    		if(order.equals("deleteLast")){
    			doubly_linked_list.removeLast();
    		}
    	}    		
		if(!doubly_linked_list.isEmpty()){
			ans.append(doubly_linked_list.getFirst());
			doubly_linked_list.removeFirst();
		}
		
		while(!doubly_linked_list.isEmpty()){
			ans.append(" ").append(doubly_linked_list.getFirst());
			doubly_linked_list.removeFirst();
		}
		System.out.println(ans.toString());
    }
}