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 C++14 (judge verdict: Time Limit Exceeded)

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <iterator>
#include <cstdio>

using namespace std;

int main() {
	int n, x;
	char com[20];
	list<int> li;
	cin >> n;
	for (int i = 0; i < n; ++i) {
		scanf("%s", com);
		if (com[0] == 'i') {
			scanf("%d", &x);
			li.push_front(x);
		} else if (com[6] == 'L') li.pop_back();
		else if (com[6] == 'F') li.pop_front();
		else if (com[0] == 'd') {
			scanf("%d", &x);
			for (int i = 0; i < li.size(); ++i) {
				if (x == *next(li.begin(), i)) {
					li.erase(next(li.begin(), i));
					break;
				}
			}
		}
	}
	int i = 0;
	while (li.size()) {
		if (i++) cout << " ";
		cout << *next(li.begin(), i);
	}
	cout << endl;


	return 0;
}