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: Time Limit Exceeded)

#include<stdio.h>
#include<string.h>
#define LEN 100005

typedef struct pp{
  char name[100];
  int t;
}P;

P Q[LEN+1];
int head, tail, n;


void enqueue(P x){
  Q[tail] = x;
  tail = (tail + 1) % LEN;
}

P dequeue(){
  P x = Q[head];
  head = (head + 1) % LEN;
  return x;
}

int min(int a,int b)
{
  if(a < b) return a;
  else return b;
}

int main(){
  int elaps = 0, c;
  int i, q;
  P u;
  scanf("%d %d", &n, &q);

  for ( i = 1; i <= n; i++){
    scanf("%s", Q[i].name);
    scanf("%d", &Q[i].t);
  }

  head = 1;
  tail = n + 1;

  while(head != tail)
    {
      u = dequeue();
      c = min(q,u.t);
      u.t -= c;
      elaps += c;
      if(u.t > 0) enqueue(u);
      else
	{
	  printf("%s %d\n",u.name,elaps);
	}
    }
  return 0;
}