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;

namespace ConsoleApplication1
{    

    class Program
    {      
        

        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            string[] input;
            string order;
            int key = 0;

            var data = new LinkedList<int>();
            
            for(int i = 0; i < n; i++)
            {
                input = Console.ReadLine().Split(' ');
                order = input[0];
                if(input.Length != 1)

                {
                    key = int.Parse(input[1]);
                }                

                if(order[0] == 'i')
                {
                    data.AddFirst(key);
                }
                else
                {
                    if(order == "delete")
                    {
                        data.Remove(key);
                    }
                    else if(order[6] == 'F')
                    {
                        data.RemoveFirst();
                    }
                    else if(order[6] == 'L')
                    {
                        data.RemoveLast();
                    }
                    
                }
            }

            Console.WriteLine(String.Join(" ", data));
            

        }
    }
}