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.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;


public class Main {
    public static void main(String[] args) throws Exception {
        
        LinkedList<String> list = new LinkedList<String>();
        String line;
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        br.readLine();
        while((line = br.readLine()) != null){
            String[] order = line.split(" ");
            switch(order[0]){
                case "insert" : list.addFirst(order[1]);
                    break;
                case "delete" : list.remove(order[1]);
                    break;
                case "deleteFirst" : list.removeFirst();
                    break;
                case "deleteLast" : list.removeLast();
                    break;
                default:
            }
        }

        String s;
        if((s = list.pollLast()) != null){
            for(String n : list)
                System.out.printf("%s ", n);
            System.out.println(s);
        }
    }
}