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++ (judge verdict: Accepted)

#include <iostream>
#include <cstdlib>
#include <list>
using namespace std;

int main() {
	list<int>L; int n, x; char s[15];
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> s;
		if (s[0] == 'i')cin >> x,  L.push_front(x);
		else if (s[6] == 'F')L.pop_front();
		else if (s[6] == 'L')L.pop_back();
		else {
			cin >> x;
			for (list<int>::iterator it = L.begin(); it != L.end(); it++)
				if (*it == x) {
					L.erase(it); break;
				}
		}
		
	}
	n = 0;
	for (list<int>::iterator it = L.begin(); it != L.end(); it++) {
		if (n++)cout << " ";
		cout << *it;
	}
	cout << endl;
	return 0;
}