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: Time Limit Exceeded)

import java.util.Scanner;
import java.util.Deque;
import java.util.ArrayDeque;

class Main {
  public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	Deque<Integer> d = new ArrayDeque<Integer>();
	
	int n = sc.nextInt();
	for(int i = 0; i < n; ++i) {
		String com = sc.next();
		int a;
		if(com.charAt(0) == 'i') {
			// insert
			a = sc.nextInt();
			d.addFirst(a);
		}else if(com.length() == 6) {
			// delete
			a = sc.nextInt();
			d.remove(a);
		}else if(com.charAt(6) == 'F') {
			// deleteFirst
			d.remove();
		}else{
			// deleteLast
			d.removeLast();
		}
	}
	
	int s = d.size();
	for(int i = 0; i < s; ++i) {
		System.out.print(i == 0 ? d.poll() : " " + d.poll());
	}
	System.out.println();
  }
}