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 Ruby (judge verdict: Wrong Answer)

n = gets.to_i
list = Array.new(n, nil)
first = 0
last = -1

n.times {
	d = gets.chomp.split(" ")
	cmd,v = d[0],d[-1]

	case cmd
	when "insert"
		last += 1
		list[last] = v.to_i
	when "delete"
		v = v.to_i
		last.downto(first) { |i|
			if list[i] == v
				list[i] = nil
				first += 1 if i == first
				last  -= 1 if i == last
				break
			end
		}
	when "deleteFirst"
		list[last] = nil
		last -= 1
	when "deleteLast"
		list[first] = nil
		first += 1
	end

	puts "  #{cmd} #{v} / first:#{first} last:#{last}"
	p list[first..last].compact.reverse

}
list = list[first..last].compact.reverse!

list.length.times { |i|
	print " " if not i == 0
	print list[i]
}
puts