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;
using System.Text;

class Program
{
    public void Proc()
    {
        int commandCount = int.Parse(Console.ReadLine());

        List<int> linear = new List<int>();

        for(int i=0; i<commandCount; i++)
        {
            string[] inpt = Console.ReadLine().Split(' ');
            int num = 0;

            if (inpt.Length >= 2)
            {
                num = int.Parse(inpt[1]);
            }

            switch (inpt[0])
            {
                case "insert":
                    linear.Add(num);
                    break;
                case "delete":
                    int idx = linear.LastIndexOf(num);
                    if(idx >=0)
                    {
                        linear.RemoveAt(idx);
                    }
                    break;
                case "deleteFirst":
                    linear.RemoveAt(linear.Count - 1);
                    break;
                case "deleteLast":
                    linear.RemoveAt(0);
                    break; 
            }
        }
        StringBuilder ans = new StringBuilder();
        for(int i=linear.Count-1; i>=0; i--)
        {
            int num = linear[i];
            if(ans.Length > 0)
            {
                ans.Append(" ");
            }
            ans.Append(num);
        }
        Console.WriteLine(ans.ToString());
        
    }

    static void Main(string[] args)

    {

        Program prg = new Program();
        prg.Proc();

    }
}