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++ (judge verdict: Time Limit Exceeded)

#include <iostream>
#include <cstdlib>
#include <cmath>
#include <cstdio>
#include <string>
#include <stack>
#include <queue>
#include <stdlib.h>
#include <sstream>
using namespace std;
string p;
int n;
int a[2000001]={};
int s, g, x;
int c;
int main()
{
    cin >> n;
    s=2000001;
    g=2000001;
    for(int i=0; i<n; i++)
    {
        cin >> p;
        if(p=="insert")
        {
            cin >> x;
            a[s-1]=x+1;
            s-=1;
        }
        else if(p=="delete")
        {
            cin >> x;
            c=0;
            for(int j=s; j<g; j++)
            {
                if((c==0)&&(a[j]==x+1))
                {
                    a[j]=0;
                    c+=1;
                }
            }
            if(a[s]==0)
            {
                s+=1;
            }
            else if(a[g-1]==0)
            {
                g-=1;
            }
        }
        else if(p=="deleteFirst")
        {
            s+=1;
        }
        else if(p=="deleteLast")
        {
            g-=1;
        }
    }
    cout << a[s]-1;
    for(int i=s+1; i<g; i++)
    {
        if(a[i]>0)
        {
            cout << " " << a[i]-1;
        }
    }
    cout << endl;
    return 0;
}