#include <bits/stdc++.h>
using namespace std;

struct node
{
   struct node* prev;
   int data;
   struct node* next;
   
}*first=NULL;
void create(int a[],int n)
{
   struct node *t,*last;
   int i;
   first=new node;
   first->data=a[0];
   first->prev=first->next=NULL;
   last=first;
   
   for(i=0;i<n;i++)
   {
      t=new node;
      t->data=a[i];
      t->next=last->next;
      t->prev=last;
      last->next=t;
      last=t;
   }
}

int lenth(struct node *p)
{
   int len=0;
   
   while(p)
   {
      len++;
      p=p->next;
   }
   return len;
}
int main()
{
	int a[]={10,20,30,40,50};
	create(a,5);
	cout<<length(first);
	display(first);
	return 0;
}