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: Time Limit Exceeded)

use std::collections::VecDeque;
//use std::io::*;
fn main(){
    let scan = std::io::stdin();
    let mut line = String::new();
    let _ = scan.read_line(&mut line);
    let vec: Vec<&str> = line.split_whitespace().collect();
    let n: i32 = vec[0].parse().unwrap();

    let mut que: VecDeque<i32> = VecDeque::new();
    for _ in 0..n{
        let mut line = String::new();
        let _ = scan.read_line(&mut line);
        let vec: Vec<&str> = line.split_whitespace().collect();
        let a: String = String::from(vec[0]);
        if a == "deleteFirst"{
            que.pop_front();
        }else if a == "deleteLast"{
            que.pop_back();
        }else{
            let b: i32 = vec[1].parse().unwrap();
            if a == "delete"{
                for x in 0..que.len(){
                    if que[x] == b{
                        que.remove(x);
                        break;
                    }
                }
            }else if a == "insert"{
                que.push_front(b);
            }
        }
    }


    {
        //let stdout = std::io::stdout();
        //let mut lock = stdout.lock();
        //let mut buf = std::io::BufWriter::new(lock);
        let x = que.pop_front();
        if x != None{
            //write!(buf, "{}",x.unwrap());
            let mut s: String = x.unwrap().to_string();
            loop{
                let x = que.pop_front();
                if x == None{
                    break;
                }
                let r: String = x.unwrap().to_string();
                s = s + " " + &r;
                //write!(buf, " {}",x.unwrap());
            }
            println!("{}",s);
        }
    }
}