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;
using System.Linq;

namespace ALDS1_3
{
    class Progarm
    {
        static void Main()
        {
            var i = new LinkedList<string>();
            var l = int.Parse(Console.ReadLine());
 
            for (var j = 0; j < l; j++)
            {
                var _t = Console.ReadLine().Split();
                 
                if (_t.Length == 1)
                {
                    if (_t[0] == "deleteFirst")
                        i.Remove(i.First);
                    else
                        i.Remove(i.Last);
                }
                else
                {
                    if (_t[0] == "insert")
                        i.AddFirst(_t[1]);
                    else
                    {
                        var node = i.First;

                        while (node != null)
                        {
                            if (node.Value == _t[1])
                            {
                                i.Remove(node);
                                break;
                            }

                            node = node.Next;
                        }
                    }
                }        
            }

            Console.WriteLine(string.Join(" ", i.ToArray()));
         }
    }
}