#include <stdio.h>
#include <alloc.h>

typedef struct l {void *info;
                  struct l *next;
                  struct l *prev;} LIST; 

void init(LIST **top, LIST **tail)
{
   *top=*tail=NULL;
}

char empty(LIST *top) 
{
   return((top==NULL) ? 1 : 0);
}

void insertright(LIST **top, LIST **tail, LIST *ptr1, void *info)
{
   LIST *ptr2=(LIST*)malloc(sizeof(LIST)); 

   if(ptr2==NULL) 
   {
      printf("Overflow");
      exit(1);
   }
   if(empty(*top))
      *top=*tail=ptr2;
   ptr2->info=info;
   ptr2->next=ptr1->next;
   ptr2->prev=ptr1;
   ptr1->next=ptr2;
}