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