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)

using System;
using System.Collections.Generic;

namespace Project
{
	
	class MainClass
	{
		public static LinkedList<int> list = new LinkedList<int>();
		public static void Main(string[] args)
		{
			int n = int.Parse(Console.ReadLine());
			for (int i = 0; i < n; i++)
			{
				string[] s = Console.ReadLine().Split(' ');
				command(s);
			}
			int m = list.Count;
			for (int i = 0; i < m; i++)
			{
				Console.Write(list.First.Value);
				list.RemoveFirst();
				Console.Write(i != m - 1 ? " " : "\n");
			}
		}

		public static void command(string[] s)
		{
			int x;
			switch (s[0])
			{
				case "insert":
					x = int.Parse(s[1]);
					list.AddFirst(x);
					break;
				case "delete":
					x = int.Parse(s[1]);
					list.Remove(x);
					break;
				case "deleteFirst":
					list.RemoveFirst();
					break;
				case "deleteLast":
					list.RemoveLast();
					break;
			}
		}
	}
}