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<iostream>
using namespace std;
#include<string.h>
#define MAX 1000000

int A[MAX], head = 0, tail = 0;

void insert(int x) {
        A[tail] = x;
        tail++;
}

void dlt(int x) {
        int a, b = 0, i;
        for(i = tail - 1; i >= head; i--) {
                if(x == A[i]) {
                        a = i; b = 1; break;
                }
        }
        if(b == 1) {
                for(int j = i; j < tail; j++) A[j] = A[j+1];
                tail--;
        }
}

int main() {
        int n, c;
        string str;
        cin >> n;
        for(int i = 0; i < n; i++) {
                cin >> str;
                if(str == "insert") {
                        cin >> c;
                        insert(c);
                }
                else if(str == "delete") {
                        cin >> c;
                        dlt(c);
                }
                else if(str == "deleteFirst") tail--;
                else head++;
        }
        for(int j = tail - 1; j >= head; j--) {
                if(j != tail - 1) cout << " ";
                cout << A[j];
        }
        cout << endl;
        return 0;
}