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 i,j,x,y,z,n=0,s,m,w=0;
  int C[2000000];
  char c[12];

  scanf("%d",&n);


  for(i=0;i<n;i++){
    scanf("%s%d",c,&y);
    if(c[0]=='i'){
      C[i]=y;
    }
    else if(c[6]=='F'){
      i-=2;
      n-=2;
    }
    else if(c[6]=='L'){
      w++;
      i--;
      n--;
    }
    else{
      m=0;
      n--;
      i--;

      for(j=i;j>=0;j--){
	if(m>0){
	    break;
	  }
	  if(y==C[j]){
	    s=i-j;
	    x=0;
	    m++;

	    while(s!=x++){
	      C[j+x-m]=C[j+x];
	    }
	    i--;
	    n--;
	  }
	  }
    }
  }

  i=0;
  while(i<n-w){
    if(i==n-w-1){
      printf("%d\n",C[n-1-i]);
    }
    else{
      printf("%d ",C[n-1-i]);
    }
    i++;
  }
  return 0;
}