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: Accepted)

#include<bits/stdc++.h>
#define ll long long 
#define P pair<int,int>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
int n,x;
string command;
deque<int> lst;

deque<int> deletex(deque<int> lst,int x){
    deque<int>::iterator it,l;
  	for(it=lst.begin(),l=lst.end();it!=l;++it){
      	if(*it == x){
          lst.erase(it);
          break;
        }
    }
    return lst;
}

int main(){
    cin >> n;
    rep(i,n){
        cin >> command;
        if(command == "insert"){
            cin >> x;
            lst.push_front(x);
        }
        if(command == "delete"){
            cin >> x;
            lst = deletex(lst,x);   
        }
        if(command == "deleteFirst"){
            lst.pop_front();
        }
        if(command == "deleteLast"){
            lst.pop_back();
        }
    }
  	deque<int>::iterator it,l;
  	
  	for(it=lst.begin(),l=--lst.end();it!=l;it++) cout << *it << " ";
    cout << *it << endl;
    return 0;
}