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: Accepted)

#include <iostream>
#include<string>
#include<list>
#include<algorithm>
using namespace std;

#define FOR(k,m,n) for(int (k)=(m);(k)<(n);(k)++)
#define REP(i,n) FOR((i),0,(n))
#define LL long long

int main() {
	int q,x;
	string command;

	
	//?¨?????????????????????????list????????¨
	list<int> value;
	cin>>q;
	REP(i, q) {
		cin>>command;
		if (command == "insert") {
			cin>>x;
			value.push_front(x);
		}
		else if (command == "deleteLast")
			value.pop_back();
		else if (command == "deleteFirst")
			value.pop_front();
		else if (command == "delete") {
			cin>>x;
			for (list<int>::iterator it = value.begin(); it != value.end(); it++) {
				if (*it == x) {
					value.erase(it);
					break;
				}
			}
		}	
	}
	//??????
	int i=0;
	for (list<int>::iterator it = value.begin(); it != value.end(); it++) {
		if(i++)cout<<" ";
		cout<<*it;
	}
	cout<<endl;
	return 0;
}