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.*;
import java.util.*;

public class Main
{
    public static void main(String[] args)
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        try{
            int i;
            int n = Integer.parseInt(br.readLine());
            ArrayDeque<String> list = new ArrayDeque<String>();
            String[] num = new String[2];
            String command;
            char c;
            for(i=0; i<n; i++)
            {
                command = br.readLine();
                c = command.charAt(0);

                if(c == 'd')
                {
                    c = command.charAt(6);
                    if(c == 'F')
                    {
                        list.pollFirst();
                    }
                    else if(c == 'L')
                    {
                        list.pollLast();
                    }
                    else
                    {
                        num = command.split(" ",0);
                        list.remove(num[1]);
                    }
                }
                else
                {
                    num = command.split(" ",0);
                    list.offerFirst(num[1]);
                }
            }

        while(list.size()>1)
        {
            System.out.printf("%d ",list.poll());
        }
        System.out.println(list.poll());
        }
        catch(Exception e)
        {
        }
    }
}