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: Time Limit Exceeded)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node{
  int num;
  struct node *next;
};
  
typedef struct node *NodePointer;


NodePointer make1node(NodePointer,int);
void showlist();
void insert(int);
void delete(int);
void deletefirst();
void deletelast();

NodePointer head;

int main(){
  int i, cou, num;
  char str[10];
  

  head = make1node(NULL, 0);
  scanf("%d", &cou);

  
  for (i = 0; i < cou; i ++){
    scanf("%s", str);
    
    if(strcmp(str, "insert") == 0){
      scanf("%d", &num);
      insert(num);
    }
    if(strcmp(str, "delete") == 0){
      scanf("%d", &num);
      delete(num);
    }
    if(strcmp(str, "deleteFirst") == 0){
      deletefirst();
    }
    if(strcmp(str, "deleteLast") == 0){
      deletelast();
    }
  }
      showlist();
  return 0;
}

NodePointer make1node(NodePointer p, int num){
  NodePointer n;
  
  n = (NodePointer)malloc(sizeof(struct node));
  n->next = p;
  n->num = num;

  return n;
}

void showlist(){
  NodePointer p;
  
  for(p = head; p->next->next != NULL; p = p->next){
    printf("%d ",p->next->num);
  }
  printf("%d", p->next->num);
  printf("\n");
}

void insert(int num){
  NodePointer new;
  new = make1node(head->next, num);
  head->next = new;
}

void delete(int num){
  NodePointer n, del;
  /*
  for (n = head; n->next != NULL; n = n->next) {
    if (n->next->num == num){
      del = n->next;
      n->next = del->next;
      free(del);
      return n;
    }
  }
  return NULL;
  */

  n = head;
  while(n->next != NULL && n->next->num != num){
    n = n->next;
  }
  if(n->next != NULL){
    del = n->next;
    n->next = n->next->next;
    free(del);
  }
}

void deletefirst(){
  NodePointer n;

  n = head->next;
  //free(head);
  head = n;
}

void deletelast(){
  NodePointer n, del;
  
  for (n = head; n->next->next != NULL; n = n->next) {
  }
  del = n->next;
  n->next = NULL;
  free(del);

}