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 a,b;

    int i,j,Ya = 0;

int f, g, h;

  scanf("%d",&a);

  int array1[a];
  char array2[12];
 
  for(i = 0;i < a;i++){
    scanf("%s %d",array2,&b);
 
    if(array2[0] == 'i'){
      array1[i] = b;
    }
 
    else if(array2[6] == 'F'){
      i -= 2;
      a -= 2;
    }
 
    else if(array2[6]=='L'){
      i--;
      a--;
      Ya++;
    }
 
    else{
      i--;
      a--;
      f = 0;
      for(j = i; j >= 0;j--){
 
	if(f > 0)break;
 
	if(b == array1[j]){
	  h = 0;
	  g = i - j;
	  f++;
	  while(g != h++)array1[j + h - 1] = array1[j + 1 + h - 1];
	  i--;
	  a--;
	}
      }
    }
  }
  for(i = 0;i < a - Ya;i++){
    if(i == a - Ya - 1)
      printf("%d\n",array1[a - 1 - i]);
    else printf("%d ",array1[a - 1 - i]);
  }
  return 0;
}