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)

def array_converter(i)
  num_array=[]
  for num in 1..i
    line = readline.split(/[[:space:]]/)
    if judge_key_and_calc(num_array,line[0],line[1])
      num_array.unshift line[1]
    end
  end
  num_array
end

def judge_key_and_calc(array,key,val)
  if key == "delete"
    if array.index(val) != nil
      array.delete_at(array.index(val))
    end
    false
  elsif key == "deleteFirst"
    array.shift
    false
  elsif key == "deleteLast"
    array.pop
    false
  else
    true
  end
end

def queue_calc
  num = readline.to_i
  array_converter(num).reverse.join(" ")
end

puts queue_calc