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