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

#define MS 1025

typedef struct dl_node
{
   char *val;
   struct dl_node *next;
   struct dl_node *prev;
} NODE;

typedef struct dl_queue
{
  NODE *start;
  NODE *end;
} QUEUE;

void insert(QUEUE *queue,FILE* folo );
void get(QUEUE *queue,char *ret_array);

main(int argc,char* argv[])
{

  clrscr();
  FILE* fp;
  char msgbuf[1025];
  int n;
  QUEUE q;
  q.start=q.end=NULL;
  n=atoi(argv[1]);
   if(argc!=3)  {
       printf("You forgot to enter the some of the data\n");
       exit(1);
    }
     if( (fp=fopen(argv[2],"r"))==NULL  )
    {
      printf("cannot open reading file\n");
      exit(1);
    }
  for(int i=0; i<n;i++)
  {
    insert(&q,fp);
  }
  while(!feof(fp))
  {
    get(&q,msgbuf);
    insert(&q,fp);
  }
  for(int j=0;j<n;j++)
  {
    get(&q,msgbuf);
    cout<<msgbuf;
  }
  return(0);
}

void insert(QUEUE *queue,FILE* folo)
{
  char temp_message[MS];
  fgets(temp_message,MS,folo);
  NODE *nn;

  nn = (NODE*) malloc (sizeof(NODE));
  nn->val =(char *) malloc( (unsigned) (strlen(temp_message) + 1));
  strcpy(nn->val,temp_message);
  nn->next = queue->start;

  if(queue->start!=NULL)
  {  queue->start->prev =nn;   }

  nn->prev = NULL;
  queue->start = nn;

  if(queue->end==NULL)
  {  queue->end = nn;  }
}

void get(QUEUE *queue,char* ret_array)
{
  NODE *temp;

  if(queue->end == NULL)
  {  return; }

 strcpy(ret_array , queue->end->val);

  if( queue->end->prev!=NULL)
   {   queue->end->prev->next = NULL; }

  temp = queue->end;
  queue->end = queue->end->prev;
  free(temp);

  if(queue->end == NULL)
   {  queue->start=NULL;  }
}