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: Memory Limit Exceeded)

import java.util.*;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		s.nextLine();
		ArrayList<Integer> seq = new ArrayList<Integer>();
		String command;
		Integer num = 0;
		while(s.hasNext()){
			String input = s.nextLine();
			String[] input_array = input.split(" ");
			if(input_array.length == 1){
				command = input_array[0];
			}
			else{
				command = input_array[0];
				num = Integer.parseInt(input_array[1]);
			}
			if(command.equals("insert")){
				seq.add(0, num);
			}
			else if(command.equals("delete")){
				seq.remove(num);
			}
			else if(command.equals("deleteFirst")){
				seq.remove(0);
			}
			else if(command.equals("deleteLast")){
				seq.remove(seq.size() - 1);
			}
		}
		s.close();
		String output = "";
		for(int i = 0; i < seq.size(); i++){
			if(i == seq.size() - 1){
				output = output + seq.get(i);
			}
			else{
				output = output + seq.get(i) + " ";
			}
			if(output.length() > 10000){
				System.out.print(output);
				output = "";
			}
		}
		System.out.println(output);

	}
}