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)

{-# LANGUAGE BangPatterns #-}

import qualified Data.Sequence as S
import Data.Sequence (Seq, (<|), (><), ViewR((:>)))
import Data.Foldable (toList)

type Op = [String]

delete :: Eq a => a -> Seq a -> Seq a
delete e s = case S.elemIndexL e s of
  Just n -> (before >< (S.drop 1 after))
    where (before, after) = S.splitAt n s
  Nothing -> s

processOp :: Seq Int -> Op -> Seq Int
processOp s op = case op of
  ["insert", num] -> read num <| s
  ["delete", num] -> delete (read num) s
  ["deleteFirst"] -> S.drop 1 s
  ["deleteLast"] -> s' where s':>_ = S.viewr s

main :: IO ()
main = do
  n <- readLn :: IO Int
  putStrLn . unwords . map show . toList =<< processloop n S.empty
  where
    processloop :: Int -> Seq Int -> IO (Seq Int)
    processloop 0 s = return s
    processloop n s = do
      op <- fmap words getLine
      processloop (n-1) $! processOp s op