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: Accepted)

n = gets.chomp!.to_i
order_list = []
n.times do
  arr = gets.chomp!.split(' ')
  order_list.push(arr)
end
linked_list = []
order_list.each do |order|
  if order[0] == "insert"
    linked_list.unshift(order[1].to_i)
  elsif order[0] == "delete"
    linked_list.each_with_index do |v, i|
      if(v == order[1].to_i)
        linked_list.delete_at(i)
        break
      end
    end
  elsif order[0] == "deleteFirst"
    linked_list.shift
  elsif order[0] == "deleteLast"
    linked_list.pop
  end
end
puts linked_list.join(' ')