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 Haskell (judge verdict: Time Limit Exceeded)

import qualified Data.Vector.Unboxed as V
import Data.List(foldl', delete)
import Data.Maybe(fromJust)

main = getContents >>= putStrLn.unwords.map show.V.toList.solve.tail.lines

solve :: [String] -> V.Vector Int
solve = foldl' solve' (V.fromList [])
    where solve' xs "deleteFirst"                 = V.tail xs
          solve' xs "deleteLast"                  = V.init xs
          solve' xs ('i':'n':'s':'e':'r':'t':_:x) = V.cons (read x) xs
          solve' xs ('d':'e':'l':'e':'t':'e':_:x) = V.fromList.delete (read x) $ V.toList xs