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: Wrong Answer)

using System;
using System.Collections.Generic;

class Program
{
	static void Main(string[] args)
	{
		int n = int.Parse(Console.ReadLine());
		List<int> list = new List<int>();
		for(int i=0; i<n; i++)
		{
			string[] input = Console.ReadLine().Split(' ');
			switch(input[0])
			{
				case "insert":
					list.Add(int.Parse(input[1]));
					break;

				case "delete":
					list.Remove(int.Parse(input[1]));
					break;

				case "deleteFirst":
					list.RemoveAt(0);
					break;

				case "deleteLast":
					list.RemoveAt(list.Count-1);
					break;
			}
		}

		list.Reverse();

		for(int i=0; i<list.Count; i++)
		{
			Console.Write((i>0 ? " " : "") + list[i]);
		}
		Console.WriteLine();
	}
}