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 JavaScript (judge verdict: Time Limit Exceeded)

var fs = require('fs');

var lines = fs.readFileSync("/dev/stdin", "utf8").split('\n');
lines.shift();
var ary = [];

var funcs = {
    'insert': insert,
    'delete': remove,
    'deleteFirst': removeFirst,
    'deleteLast': removeLast
};

var length = 0;

lines.forEach(function(l) {
    var spl = l.split(' ');
    var inst = spl[0];
    var arg = spl[1];

    funcs[inst] && funcs[inst](arg);
});

console.log(ary.join(' '));

function insert(n) {
    ary.unshift(parseInt(n));
    length ++;
};

function remove(n) {
    for(var i = 0; i < length; i++) {
        if (ary[i] == n) {
            ary.splice(i, 1);
            length--;
            return;
        }
    }
}

function removeFirst() {
    ary.shift();
    length--;
}

function removeLast() {
    ary.pop();
    length--;
}