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>


/*-----------構造体定義-----------------*/
typedef struct node{
 int num;
 struct node *left;
 struct node *right;
}node;
/*--------------------------------------*/


/*-----------------要素作成-------------*/
node* makenode(int x){
node* new;

new=(node*)malloc(sizeof(node));
new->num=x;
new->right=NULL;

return new;
}
/*-------------------------------------*/


int main(){
int n,i,x;
int y=1;
char com[13];
node* root;
node* p;
node** q;
node* r;
root=NULL;

scanf("%d",&n);

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

 if(com[0]=='i'){
   scanf("%d",&x);
   p=makenode(x);
    if(root!=NULL){
        root->left=p;
        p->right=root;
        root=p;
    }else{root=p;}
 }else
 if(strcmp(com,"deleteFirst")==0){
   if(root->right==NULL){free(root);root=NULL;}
   else{root->right->left=NULL;
        root=root->right;}
  }else
  if(strcmp(com,"deleteLast")==0){
   if(root->right==NULL){root=NULL;}
   else{q=&(root->right);
    while((*q)!=NULL){
     if((*q)->right==NULL){(*q)=NULL;}
     else{q=&((*q)->right);}
    }
   }
  }else
  

if(strcmp(com,"delete")==0){
   scanf("%d",&x);

/*要素1つの場合*/
if(root->right==NULL){if(root->num==x)root=NULL;}

/*要素が2以上*/
else{

  if(root->num==x){/*先頭*/
       root->right->left=NULL;
       root=root->right;}

  else{p=root;
  
      while(p!=NULL){

        if(p->num==x){

          if(p->right==NULL){p->left->right=NULL;break;}
          else{

            p->right->left=p->left;
            p->left->right=p->right;
            p->right=NULL;}
        }

        p=p->right;


       }/*while終了*/


   }
}
}
}
p=root;
while(p!=NULL){

if(p->right==NULL){printf("%d\n",p->num);}
else{printf("%d ",p->num);}
p=p->right;

}



return 0;
}