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 Rust (judge verdict: Accepted)

use std::io::Read;
use std::collections::LinkedList;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    let mut iterator = buf.split_whitespace();


    let mut ll = LinkedList::new();

    let n: usize = iterator.next().unwrap().parse().unwrap();
    for _i in 0..n {
        let command = iterator.next().unwrap();

        if command == "insert" {
            let key: u64 = iterator.next().unwrap().parse().unwrap();
            ll.push_front(key)
        } else if command == "delete" {
            let key: u64 = iterator.next().unwrap().parse().unwrap();
            let position = ll.iter().position(|&it| it == key);
            if let Some(position) = position {
                let mut tail = ll.split_off(position);
                tail.pop_front();
                ll.append(&mut tail);
            }
        } else if command == "deleteFirst" {
            ll.pop_front();
        } else if command == "deleteLast" {
            ll.pop_back();
        }
    }

    let mut result = String::new();
    for k in ll {
        result += &format!("{} ", k);
    }

    println!("{}", result.trim());
}