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: Runtime Error)

class DoublyLinkedList
  def initialize
    @data = []
  end

  def insert(x)
    @data.unshift x
  end

  def delete(x)
    @data.delete_at(@data.index(x))
  end

  def delete_first
    @data.shift
  end

  def delete_last
    @data.pop
  end

  def description
    @data.join(" ")
  end
end

list = DoublyLinkedList.new
n = gets.to_i
(1..n).each {
  op, x = gets.split(" ")
  case op
    when "insert" then list.insert(x.to_i)
    when "delete" then list.delete(x.to_i)
    when "deleteFirst" then list.delete_first
    when "deleteLast" then list.delete_last
  end
}

puts list.description