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::str::FromStr;
use std::collections::{HashMap,HashSet,VecDeque,BinaryHeap};
use std::cmp::{max,min,Ordering};
use std::io::Read;

fn main() {

    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    let mut buf_it = buf.split_whitespace();

    let N = buf_it.next().unwrap().parse::<usize>().unwrap();

    let mut V = VecDeque::new();

    for _ in 0..N{
        let c = buf_it.next().unwrap();
        match c{
            "insert" => {
                let n = buf_it.next().unwrap().parse::<usize>().unwrap();
                V.push_front(n);
            },
            "delete" => {
                let n = buf_it.next().unwrap().parse::<usize>().unwrap();
                let mut j = N+10;
                for (i,&v) in V.iter().enumerate(){
                    if n==v{
                        j = i;
                        break;
                    }
                }
                V.remove(j);
            },
            "deleteFirst" => {
                V.pop_front();
            },
            "deleteLast" => {
                V.pop_back();
            },
            _ => {}
        }
    }
    
    println!("{}",V.iter().map(|v| format!("{}",v)).collect::<Vec<_>>().join(" "));
}