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;
class ilds1_3_c{
  public static void Main(){
    int n = int.Parse(Console.ReadLine());
    LinkedList<String> list = new LinkedList<String>();
    for(int i=0; i<n; i++){
      String[] str = Console.ReadLine().Split(' ');
      switch(str[0]){
        case "insert":
          list.AddFirst(str[1]);
          break;
        case "delete":
          list.Remove(str[1]);
          break;
        case "deleteFirst":
          list.RemoveFirst();
          break;
        case "deleteLast":
          list.RemoveLast();
          break;
      }
    }
    Console.WriteLine(string.Join(" ",list));
  }
}