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 a = int.Parse(Console.ReadLine());
        List<int> s = new List<int>(new int[]{ });
        int saigonannbannme = 0;
        int addor = 0;
        for (int i = 0; i < a; i++)
        {
            string[] s2 = Console.ReadLine().Split();
            if (s2.Length == 2)
            {
                addor = int.Parse(s2[1]);
            }
            if (s2[0] == "insert")
            {
                s.Add(addor); saigonannbannme++;
            }
            else if (s2[0] == "delete")
            {
                s.Remove(addor); saigonannbannme--;
            }
            else if (s2[0] == "deleteFirst")
            {
                s.Remove(s[0]); saigonannbannme--;
            }
            else if (s2[0] == "deleteLast")
            {
                s.Remove(s[saigonannbannme - 1]); saigonannbannme--;
            }
        }
        for (int i = saigonannbannme - 1; i >= 0; i--)
        {

            if (i == 0) { Console.WriteLine(s[i]); }

            if (!(i == 0))
            {
                Console.Write(s[i]);
                Console.Write(" ");
            }
        }
        Console.ReadLine();

    }
}