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 JAVA (judge verdict: Wrong Answer)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

public class Main {

	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		
		int x=Integer.parseInt(br.readLine());
		ArrayList<Integer> list=new ArrayList<Integer>();
		for (int i = 0; i < x; i++) {
			//System.out.println(list);
			String s=br.readLine();
			String[] v=s.split(" ");
			if(v[0].equals("insert")){
				int val=Integer.parseInt(v[1]);
				list.add(val);
			}else if(v[0].equals("delete")){
				int val=Integer.parseInt(v[1]);
				for (int j = 0; j < list.size(); j++) {
					if(list.get(j)==val){
						list.remove(j);
						break;
					}
				}
				
			}else if(v[0].equals("deleteLast")){
				list.remove(0);
				
			}else if(v[0].equals("deleteFirst")){
				int size=list.size()-1;
				list.remove(size);
			}
		}
		for (int i = list.size()-1; i >= 0; i--) {
			System.out.print(list.get(i));
			if(i>0)
				System.out.print(" ");
		}
		System.out.println();

	}

}