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

# 双方向連結リストの実装
N = int(input())
commands = [input() for _ in range(N)]

d = deque()

for c in commands:
    if c == "deleteFirst":
        if d:
            d.popleft()

    elif c == 'deleteLast':
        if d:
            d.pop()

    elif 'delete ' in c:
        _, key = c.split()
        key = int(key)
        if key in d:
            d.remove(key)

    elif 'insert ' in c:
        _, key = c.split()
        key = int(key)
        d.appendleft(key)

print(*d)