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 C++11 (judge verdict: Time Limit Exceeded)

#include <bits/stdc++.h>

#define REP(i, n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()
#define square(x) (x) * (x)
#define cube(x) (x) * (x) * (x)

const int INF = 1e9;

using namespace std;

int main() {
    int n;
    list<int> a;
    cin >> n;
    REP(i, n){
        string ope;
        cin >> ope;
        if(ope[0] == 'i'){
            int x;
            cin >> x;
            a.push_front(x);
        } else if(ope[6] == 'F'){
            a.pop_front();
        } else if(ope[6] == 'L') {
            a.pop_back();
        } else if(ope[0] == 'd') {
            int x;
            cin >> x;
            for(list<int>::iterator s = a.begin(); s != a.end(); s++){
                if(*s == x){
                    a.erase(s);
                    break;
                }
            }
        }
    }

    list<int>::iterator s = a.begin();
    for(int i=0;i<a.size()-1;i++){
        cout << *s << " ";
        s++;
    }
    cout << *s << endl;

    return 0;
}