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, w, i, j, y=0, l, m, k;
  scanf("%d", &n);
  int data[n];
  char c[12];

  for(i = 0; i < n; i++){
    scanf("%s %d", c, &w);

    if(c[0] == 'i'){
      data[i]=w;
    }

    else if(c[6] == 'F'){
      i -= 2;
      n -= 2;
    }

    else if(c[6] == 'L'){
      i--;
      n--;
      y++;
    }

    else{
      i--;
      n--;
      l=0;
      for(j = i; j >= 0; j--){

    if(l > 0) break;

    if(w == data[j]){
      k = 0;
      m = i-j;
      l++;
      while(m!=k++)
    data[j + k - 1]=data[j + 1 + k - 1];
      i--;n--;
    }
      }
    }
  }
  for(i = 0; i < n-y; i++){
    if(i == n-y-1)
      printf("%d\n",data[n-1-i]);
    else
      printf("%d ",data[n-1-i]);
  }
  return 0;
}