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)

# coding: utf-8
import sys
from collections import deque

output_str = deque()
data_cnt =  int(input())  

for i in range(data_cnt):
    in_command = input().rstrip().split(" ")
    
    if in_command[0] == "insert":
        output_str.appendleft(in_command[1])
    elif in_command[0] == "delete":
        try:
            output_str.remove(in_command[1])
        except:
            pass
    elif in_command[0] == "deleteFirst":
        output_str.popleft()
    elif in_command[0] == "deleteLast": 
        output_str.pop()

print(" ".join(output_str))