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 Ruby (judge verdict: Wrong Answer)

n = gets.chomp.to_i
queue = Array.new
n.times do
  order = gets.split(" ")
  case order[0]
    when "insert"
      queue.unshift(order[1].to_i)
    when "delete" && (queue.index(order[1].to_i) != nil)
      queue.delete_at(queue.index(order[1].to_i))
    when "deleteFirst"
    queue.shift
    when "deleteLast"
    queue.pop
  end
end
(queue.size).times do |num|
  print queue[num]
  num+1 == (queue.size) ? (print "\n") : (print " ")
end