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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {
	
	public static void main(String arg[]){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		List<Integer> list = new ArrayList<Integer>();
		String sta;  /*Statement*/
		int num = 0;
		int cnt = 0;

		
		for(int i=0; i<N; i++){
			sta = sc.next();
			
			if(sta.equals("insert")){
				num = sc.nextInt();
				list.add(0, num);
			}else if(sta.equals("delete")){
				num = sc.nextInt();
				if(list.indexOf(num)>=0){
					list.remove(list.indexOf(num));
				}
			}else if(sta.equals("deleteFirst")){
				list.remove(0);
			}else if(sta.equals("deleteLast")){
				list.remove(list.size()-1);
			}
		}
		for (int i=0; i<list.size()-1; i++){
	        System.out.print(list.get(i) + " ");
		}
		System.out.println(list.get(list.size()-1));
	}
}