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,i,j;
    int 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+h];		  
		    }
		    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;
}