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;

class Program
{
	static int[] array = new int[0];

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

		for(int i=0; i<n; i++)
		{
			string[] input = Console.ReadLine().Split(' ');
			switch(input[0])
			{
				case "insert":
					AddArray(int.Parse(input[1]));
					break;

				case "delete":
					for(int j=array.Length-1; j>=0; j--)
					{
						if(array[j] == int.Parse(input[1]))
						{
							array[j] = -1;
							RemoveArray(j);
							break;
						}
					} 
					break;

				case "deleteFirst":
					for(int j=array.Length-1; j>=0; j--)
					{
						if(array[j] != -1)
						{
							array[j] = -1;
							RemoveArray(j);
							break;
						}
					}
					break;

				case "deleteLast":
					for(int j=0; j<array.Length; j++)
					{
						if(array[j] != -1)
						{
							array[j] = -1;
							RemoveArray(j);
							break;
						}
					}
					break;
			}
		}

		bool is_space = false;
		for(int i=array.Length-1; i>=0; i--)
		{
			if(array[i] != -1)
			{
				Console.Write((is_space ? " " : "") + array[i]);
				is_space = true;
			}
			
		}
		Console.WriteLine();
	}

	static void AddArray(int input)
	{
		int size = array.Length + 1;
		int[] buf = new int[size];
		for(int i=0; i<array.Length; i++)
		{
			buf[i] = array[i];
		}
		buf[size-1] = input;
		array = new int[size];
		Array.Copy(buf, array, buf.Length);
	}

	static void RemoveArray(int n)
	{
		int size = array.Length - 1;
		int[] buf = new int[size];
		for(int i=0; i<n; i++)
		{
			buf[i] = array[i];
		}
		for(int i=n; i<buf.Length; i++)
		{
			buf[i] = array[i+1];
		}
		array = new int[size];
		Array.Copy(buf, array, buf.Length);
	}
}