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 <vector>
#include <deque>
#include <list>
#include <forward_list>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <tuple>
#include <functional>
#include <limits>
#include <utility>
#include <string>
#include <sstream>
#include <iostream>

#define DEBUG

using namespace std;

// Print each element of a container.
template <typename Container>
void print(const Container& container)
{
#ifdef DEBUG

	string delim("");

	for (const auto& element : container)
	{
		cout << delim << element;
		delim = " ";
	}

	cout << endl;

#endif
}

int main()
{
	list<int> list;

	int n;
	cin >> n;

	for (size_t i(0); i < n; ++i)
	{
		string command;
		cin >> command;

		if (command == "insert") 
		{ 
			int x;
			cin >> x; 

			list.push_front(x); 
		}
		else if (command == "delete")
		{
			int x;
			cin >> x; 

			auto it(find(begin(list), end(list), x)); 

			if(it != end(list))
			{
				list.erase(it);
			} 
		}
		else if (command == "deleteFirst")
		{
			list.pop_front();
		}
		else if (command == "deleteLast")
		{
			list.pop_back();
		}
	}

	print(list);

	return 0;
}