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 PHP (judge verdict: Wrong Answer)

<?php
fscanf(STDIN, '%d', $length);
$list = array();

for($i=0; $i<$length; ++$i){
    fscanf(STDIN, '%s %s', $action, $str);
    switch ($action) {
    case 'insert':
        array_unshift($list,$str);
        break;
    case 'delete':
        $key=array_search($str, $list);
        echo("key".$key);
        if(isset($key)){
            print("なんで".$list[$key]);
            unset($list[$key]);
        }
        if($key==0){
            print("aaa");
            // print($list[$key]);
        }
        break;
    case 'deleteFirst':
        array_shift($list);
        break;
    case 'deleteLast':
        array_pop($list);
        break;
    }
}

echo implode(" ",$list) . PHP_EOL;