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
import sys
n = int(input())
deq = deque()
sub_deq = {}
for cmd in sys.stdin.readlines():
    if cmd == 'deleteFirst\n':
        while deq:
            data = deq.pop()
            if data[1]:
                data[1] = 0
                break
    elif cmd == 'deleteLast\n':
        while deq:
            data = deq.popleft()
            if data[1]:
                data[1] = 0
                break
    else:
        cmd, val = cmd.split()
        if cmd == 'insert':
            data = [val, 1]
            deq.append(data)
            if val not in sub_deq:
                sub_deq[val] = [data]
            else:
                sub_deq[val].append(data)
        elif cmd == 'delete':
            if val in sub_deq:
                deq_v = sub_deq[val]
                while deq_v:
                    data = deq_v.pop()
                    if data[1]:
                        data[1] = 0
                        break
sys.stdout.write(" ".join(data[0] for data in reversed(deq) if data[1]))
sys.stdout.write('\n')