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)

#define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
#include <list>
#include <utility>
#include <numeric>

using namespace std;

int main()
{
	list<int> v;

	int n;
	for (cin >> n; n--;)
	{
		string s;
		int x;
		cin >> s;

		if (s == "insert")
		{
			cin >> x;
			v.push_front(x);
		}
		else if (s == "delete")
		{
			cin >> x;
			for (list<int>::iterator it = v.begin(); it != v.end(); it++)
			{
				if (*it == x)
				{
					v.erase(it);
					break;
				}
			}
		}
		else if (s == "deleteFirst")
		{
			v.pop_front();
		}
		else if (s == "deleteLast")
		{
			v.pop_back();
		}
	}

	bool space = false;
	for (list<int>::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << (space ? " " : "");
		space = true;

		cout << *it;
	}

	cout << endl;
}