#include<stdio.h>
#include<stdlib.h>
typedef struct pointer
         { int info;
           struct pointer *lptr;
           struct pointer *rptr;
         } dslr;
dslr *l,*r,*p, *M;

int main()
{
    int a, i, x;
    printf("\n Nhap so phan tu cua day: ");
    scanf("%d",&a);
    if(a==0) printf("\n Day rong");
    else
{
    //tao ds
    dslr *p, *l, *r, *m, *n;
    m=NULL;
    n=NULL;
    for(i=1;i<=a;i++) //phat trien sang ben phai
    {
        p=(dslr*)malloc(sizeof(dslr));
        if(m==NULL)
        {
            p->lptr=NULL;
            m=p;
        }
        else
        {
            p->lptr=m;
            m=p;
        }
    }
    r=p;// dua r ve cuoi ds

    for(i=1;i<=a;i++) //phat trien sang ben trai
    {
        if(n==NULL)
        {
            p->rptr=NULL;
            n=p;
        }
        else
        {
            p->rptr=n;
            n=p;
        }

        if(i<a)
        {
            p=p->lptr;
        }
    }
    l=p;     // dua l len dau ds

    for(i=1;i<=a;i++) //nhap info cho ds, sau buoc nay p tro ve cuoi ds
    {
        printf("\n Nhap phan tu thu %d: ",i);
        scanf("%d", &p->info);
        p=p->rptr;
    }
    p=l; // dua p tro ve dau de in ra kq,  sau buoc nay p tro ve cuoi ds
    printf("\n Day vua nhap la: ");
    for(i=1;i<=a;i++)
    {
        printf("  %d",p->info);
        p=p->rptr;
    }


    //them vao dau d.s
    printf("\n Gia tri phan tu muon bo sung vao dau d.s: ");
    scanf("%d",&x);

    M=l; //m o dau ds
    p=(dslr*)malloc(sizeof(dslr));
    p->info=x;
        p->lptr=NULL;
        p->rptr=M;
        M->lptr=p;
        l=p;

    printf("\n Day sau khi bo sung vao dau la: ");
    for(i=1;i<=a+1;i++)
    {
        printf("  %d",p->info);
        p=p->rptr;
    }


    //them cuoi
    printf("\n Gia tri phan tu muon bo sung vao cuoi d.s: ");
    scanf("%d",&x);
    M=r;
    p=(dslr*)malloc(sizeof(dslr));
    p->info=x;
        p->rptr=NULL;
        p->lptr=M;
        M->rptr=p;
        r=p;
        p=l;
        printf("\n Day sau khi bo sung vao cuoi la: ");
    for(i=1;i<=a+2;i++)
    {
        printf("  %d",p->info);
        p=p->rptr;
    }

    //xoa nut cuoi
    M=r;
    r=r->lptr;
    r->rptr=NULL;
    M->lptr=NULL;
    printf("\n Day sau khi xoa nut cuoi: ");
    p=l;
    for(i=1;i<=a+1;i++)
    {
        printf("  %d",p->info);
        p=p->rptr;
    }

    //xoa nut dau

    M=l;
    l=l->rptr;
    l->lptr=NULL;
    M->rptr=NULL;
    printf("\n Day sau khi xoa nut dau: ");
    p=l;
    for(i=1;i<=a;i++)
    {
        printf("  %d",p->info);
        p=p->rptr;
    }

    //tim phan tu chan dau tien
    p=l;
    int t;
    while(p!=NULL)
    {
        if(p->info%2==0)
        {
            t=p->info;
            break;
        }
        p=p->rptr;
    }

    if(p!=NULL)printf("\n Phan tu chan dau tien la : %d",p->info);
    else printf("\n Khong co phan tu chan nao");

}
return 1;
}