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: Memory Limit Exceeded)

import Data.List (foldl',delete)
import Control.Monad (replicateM)
import qualified Data.ByteString.Char8 as C

main = do
  n <- readLn
  s <- replicateM n C.getLine
  let xs = foldl' test [] s
  putStrLn $ C.unpack $ C.unwords xs

test :: [C.ByteString] -> C.ByteString -> [C.ByteString]
test xs s
  | s == (C.pack "deleteFirst")  = tail xs
  | s == (C.pack "deleteLast")   = init xs
  | 'i' `elem` (C.unpack s)      = x : xs
  | otherwise         = delete x xs
  where
    x = (C.words s) !! 1