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 <stdio.h>
 
#if 1
#define gc() getchar_unlocked()
#define pc(c) putchar_unlocked(c)
#else
#define gc() getchar()
#define pc(c) putchar(c)
#endif
 
int in()
{
	int n = 0, c = gc();
	do n = 10*n + (c & 0xf), c = gc(); while (c >= '0');
	return n;
}
 
void skip(int k) { while (k--) gc(); }
 
void out(int n)
{
	int i;
	char ob[20];
 
	if (!n) { pc('0'); return; }
	i = 0; while (n) ob[i++] = n%10 + '0', n/=10;
	while (i--) pc(ob[i]); 
}
 
int que[1500005]; int top, end;
 
int main()
{
	int n, i, t;
	char op;
 
	n = in(); top = 0, end = 1;
	while (n--) {
		if (gc() == 'i') {
			skip(6);
			que[end++] = in();
		} else {
			skip(5);
			op = gc();
			if (op == 'L') {
				skip(4);
				top++;
			} else if (op == 'F') {
				skip(5);
				end--;
			} else {
				que[top] = t = in();
				i = end; while (que[--i] != t);
				if (i > top) {
					if (end - i < i - top) {
						while (++i < end) que[i-1] = que[i];
						end--;
					} else {
						while (--i > top) que[i+1] = que[i];
						top++;
					}
				}
			}
		}
	}
	i = end-1; out(que[i--]);
	while (i > top) pc(' '), out(que[i--]);
	pc('\n');
	return 0;
}