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>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n)   FOR(i,0,n)
#define pb emplace_back
typedef long long ll;
typedef pair<int,int> pint;

list<int> ls;
int main(){
    ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int n,x;
    cin>>n;
    string s;
    rep(i,n){
        cin>>s;
        if(s=="insert"){
            cin>>x;ls.push_front(x);
        }
        else if(s=="deleteFirst") ls.pop_front();
        else if(s=="deleteLast") ls.pop_back();
        else{
            cin>>x;
            for(list<int>::iterator it=ls.begin();it!=ls.end();++it){
                if(*it==x){
                    ls.erase(it);
                    break;
                }
            }
        }
    }
    int cnt=0;
    for(list<int>::iterator it=ls.begin();it!=ls.end();++it){
        cout<<*it<<(cnt+1==ls.size()?"":" ");
        ++cnt;
    }
    cout<<endl;
    return 0;
}