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)

/*http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_3_C&lang=jp*/

#include <cstdio>
#include <list>
#include <cstring>

using namespace std;

int main(){
    int n;
    list<int> data;

    scanf("%d",&n);
    for(int i=0;i<n;i++){
        char command[15];
        scanf("%15s",command);
        if(command[0]=='i'){
            int j;
            scanf("%d",&j);
            data.push_front(j);
        }else if(command[0]=='d'){
            if(command[6]=='F'){
                data.pop_front();
            }else if(command[6]=='L'){
                data.pop_back();
            }else{
                int j;
                scanf("%d",&j);
                list<int>::iterator it=data.begin();
                while(*it!=j){
                    it++;
                }
                data.erase(it);
            }
        }
    }
    for(int i=0;0<data.size();i++){
        printf("%d",data.front());
        data.pop_front();
        if(0<data.size()){
            printf(" ");
        }
    }
    printf("\n");
    return 0;
}