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++14 (judge verdict: Time Limit Exceeded)

#include <algorithm>
#include <cctype>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <list>
#include <queue>
#include <sstream>
#include <stack>
#include <string>
#include <vector>

#define REP(i,n) for(int i=0;i<n;++i)
#define RREP(i,n) for(int i=n-1;i>=0;--i)
#define FOR(i,m,n) for(int i=m;i<n;++i)
#define RFOR(i,m,n) for(int i=m-1;i>=n;--i)
#define ALL(v) v.begin(),v.end()
#define pb(a) push_back(a)
#define INF 1000000001
#define MOD 1000000007

using namespace std;



int main() {
	int n;
	list<int> l;
	cin >> n;
	REP(i, n) {
		string s;
		cin >> s;
		if (s == "insert") {
			int x;
			cin >> x;
			l.push_front(x);
		}
		else if (s == "delete") {
			int x;
			cin >> x;
			for (auto itr = l.begin();itr != l.end();++itr) {
				if (*itr == x) {
					l.erase(itr);
					break;
				}
			}
		}
		else if (s == "deleteFirst") {
			l.pop_front();
		}
		else {
			l.pop_back();
		}
		
	}
	int i = 0;
	auto itr = l.begin();
	cout << *itr;
	itr++;
	while (itr != l.end()) {
		cout << " " << *itr;
		itr++;
	}
	cout << endl;
	return 0;
}