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<list>
using namespace std;
int main() {
	list<int> line;
	int code;
	char codename[11];
	int time;
	cin >> time;
	list<int >::iterator he;
	for (int i = 0; i < time; ++i) {
		cin >> codename;
		if (codename[6] == 'F')line.pop_front();
		else if (codename[6] == 'L')line.pop_back();
		else {
			cin >> code;
			if (codename[0] == 'i')line.push_front(code);
			else {
				line.push_back(code);
				for (he = line.begin(); *he != code; ++he);
				if (++he != line.end())line.erase(--he);
				line.pop_back();
			}
		}
	}
	int doll = line.back();
	line.pop_back();
	for (he = line.begin(); he != line.end(); ++he) {
		cout << *he << ' ';
	}
	cout << doll << endl;
	cin >> time;
	return 0;
}