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 Python (judge verdict: Runtime Error)

import sys

l = []

n = int(sys.stdin.readline().strip())

def delete(lst,x):
	lst.remove(x)

def deleteFirst(lst):
	lst.pop(0)
def deleteLast(lst):
	lst.pop(len(lst)-1)
for i in range(n):
	c = sys.stdin.readline().strip().split(" ")
	if c[0]=="insert":
		l.append(int(c[1]))
	elif c[0]=="delete":
		delete(l,int(c[1]))
	elif c[0]=="deleteFirst":
		deleteFirst(l)
	elif c[0]=="deleteLast":
		deleteLast(l)

for a in l[::-1]:
	print(a),