#include<stdio.h>
#include<conio.h>
#include<alloc.h>
typedef struct pointer
         { int info;
           struct pointer *LPTR;
		   struct pointer *RPTR;
         } ds;
ds *l,*r,*q,*M,*p;
int n,i,m,d;
void main()
{
	printf(" Nhap vao so phan tu muon nhap n= ");
	scanf("%d",&n);
	l=NULL;r=NULL;
	for(i=1;i<=n;i++)
	{
		q=(ds *)malloc(sizeof(ds));
		printf("\n phan tu thu %d ",i);
		scanf("%d",&q->info);
		if(l==NULL)
		{
			q->LPTR=NULL;
			q->RPTR=NULL;
			l=r=q;
		}
		else
		{
			q->LPTR=NULL;
			q->RPTR=l;
			l->LPTR=q;
			l=q;
		}
	}
	printf("hay nhap tu ban phim , thu tu phan tu muon tro toi \n");
	printf("chu y rang , so can nhap phai nho hon hoac bang %d ",n);
	printf("m = ");
	do
	{
		scanf("%d",&m);
	}while(m>n);
	q=r;d=1;
	while(d<m)
	{
		q=q->LPTR;d++;
	}
	M=q;
	p=(ds*)malloc(sizeof(ds));
	printf(" Hay nhap gia tri phan tu muon bo sung sau con tro M ");
	scanf("%d",&p->info);
	if(M==r)
	{
		p->RPTR=NULL;
		p->LPTR=r;
		r->RPTR=p;
		r=p;
	}
	else
    {
    	p->LPTR=M;
		p->RPTR=M->RPTR;
		M->RPTR=p;
		p->RPTR->LPTR=p;
    }
	n++;
	printf("ta co danh sach sau khi them vao phan tu moi gom %d phan tu \n ",n);
	q=r;
	while(q!=NULL)
	{
		printf("%d",q->info);
		q=q->LPTR;
	}
	// xoa phan tu duoc tro boi M
	if(M==l)
	{
		l=l->RPTR;
		l->LPTR=NULL;
		M->RPTR=NULL;
	}
	else
	{
		M->LPTR->RPTR=M->RPTR;
		M->RPTR->LPTR=M->LPTR;
	}
	free(M);
	printf("\n danh sach sau khi da bo di 1 phan tu duoc tro boi con tro M la :\n ");
	q=r;
	while(q!=NULL)
	{
		printf("%d",q->info);
		q=q->LPTR;
	}
	getch();
}