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)

#![allow(non_snake_case)]

use std::io;
use std::io::prelude::*;
use std::collections::VecDeque;

fn main() {
    let sin = io::stdin();
    let mut l_iter = sin.lock().lines();
    let _n = l_iter.next().unwrap().unwrap().parse::<usize>().unwrap();

    let mut que = VecDeque::new();

    for line in l_iter {
        let l = line.unwrap();
        let mut ws = l.split_whitespace();
        match ws.next().unwrap() {
            "insert" => { 
                let d: u32 = ws.next().unwrap().parse().unwrap();
                que.push_front(d);
            },
            "delete" => { 
                let d: u32 = ws.next().unwrap().parse().unwrap();
                let mut res = None;
                for (i, v) in que.iter().enumerate() {
                    if d == *v {
                        res = Some(i);
                        break;
                    }
                }
                if let Some(idx) = res {
                    que.remove(idx);
                }
            },
            "deleteLast" => { 
                que.pop_back(); 
            },
            "deleteFirst" => { 
                que.pop_front(); 
            },
            _ => {;},
        }
    }

    let s = que.iter().map(|v| v.to_string())
        .collect::<Vec<String>>()
        .join(" ");
    println!("{}", s);
}