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.to_i
a=Array.new
h=Hash.new
n.times{
  com=gets.split(' ').map(&:to_s)
  case com[0]
  when 'insert'
     a.push(com[1].to_i)
     h[com[1].to_i]=a.length-1
  when 'delete'
     pi=h[com[1].to_i]
     if pi==nil then
        i=a.rindex(com[1].to_i)
        if i!=nil then
           a.delete_at(i)
        end
     else
        a.delete_at(pi)
     end
  when 'deleteFirst'
     if a.length>0 then
     a.delete_at(a.length-1)
     end
  when 'deleteLast'
     if a.length>0 then
     a.delete_at(0)
     end
  end
}
r=a.reverse.join(' ')
printf("%s\n", r)