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>
 
int main()
{
  int i,j,r,s,x,y,z,num = 0;
 
  char c[12];
  
  scanf("%d",&r);

   int array[r];
  
  for(i = 0;i < r;i ++)
    {
      scanf("%s %d",c,&s);
      if(c[0] == 'i')
	{
	  array[i] = s;
	}
      else if(c[6] == 'F')
	{
	  i -= 2;
	  r -= 2;
	}
      else if(c[6] == 'L'){
	i --;
	r --;
	num ++;
      }
      else{
	i --;
	r --;
	x = 0;
      
	for(j = i;j >= 0;j --){

	  if(x > 0)break;
	
	  if(s == array[j]){
	    y = i - j;
	    z = 0;
	    x ++;
	    while(y != z){
	      z ++;
	      array[j + z - 1] = array[j + 1 + z - 1];
	    }
	  
	    i --;
	    r --;
	  }
	}
      }
    }
  
  for(i = 0;i < r - num;i ++)
    {
      if(i == r - num - 1)printf("%d\n",array[r - 1 - i]);
      else printf("%d ",array[r - 1 - i]);
    }
  return 0;
}