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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
 
class Program
{
    static void Main()
    {
        int c = int.Parse(Console.ReadLine());
        LinkedList<int> l = new LinkedList<int>();
         
        for (int i=0; i<c; i++)
        {
            string[] s = Console.ReadLine().Split(' ');
            int n = 0;
             
            if (s.Length>1) { n = int.Parse(s[1]); }
             
            if (s[0].Equals("insert"))
            {
                l.AddFirst(n);
            } 
            else if (s[0].Equals("delete"))
            {
                if (l.Contains(n))
                {
                    l.Remove(n);
                }
            }
            else if (s[0].Equals("deleteFirst"))
            {
                if (l.Count>0) l.RemoveFirst();
            }
            else if (s[0].Equals("deleteLast"))
            {
                if (l.Count>0) l.RemoveLast();
            }
        }
         
        string ret = "";
         
        foreach (int n in l) { ret = ret + n.ToString() + " "; }
        Console.WriteLine(ret.TrimEnd());
    }
}