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 Python3 (judge verdict: Accepted)

from collections import deque
from enum import Enum
import sys
import math

BIG_NUM = 2000000000
MOD = 1000000007
EPS = 0.000000001


LIST = deque()

num_command = int(input())

for loop in range(num_command):

    input_command = input()

    if input_command == 'deleteFirst':
        LIST.popleft()
    elif input_command == 'deleteLast':
        LIST.pop();
    else:
        com,num = input_command.split()

        if com == 'insert':
            LIST.appendleft(num)
        elif com == 'delete':
            try:
                LIST.remove(num)
            except:
                pass

print(' '.join(LIST))