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)

const config = {
    input: '/dev/stdin',
    newline: '\n'
};

const line = require('fs').readFileSync(config.input, 'utf-8').split(config.newline);

const insert = (arr, x) => arr.unshift(x);
const del = (arr, x) => {
    const index = arr.indexOf(x);
    if (index >= 0) {
        arr.splice(index, 1);
    }
};
const delFirst = arr => arr.shift();
const delLast = arr => arr.pop();

const cmds = line.slice(1);
const ans = cmds.reduce((acc, x) => {
    const cmd = x.split(' ');
    switch (cmd[0]) {
        case 'insert':
            insert(acc, parseInt(cmd[1]));
            break;
        case 'delete':
            del(acc, parseInt(cmd[1]));
            break;
        case 'deleteFirst':
            delFirst(acc);
            break;
        case 'deleteLast':
            delLast(acc);
            break;
    }

    return acc;
}, []).map(x => x.toString()).join(' ');

console.log(ans);