n个人围成一圈，从第一个人起，1，2，3的循环，拿到三号的退出，问最后剩下的是原来的几号？

/* Note:Your choice is C IDE */
#include "stdio.h"
#define NULL 0
#define LEN sizeof(struct student)
struct student
{
    int num;
    struct student *next;
};
int n;
struct student *creat(void)
{
    struct student *head;
    struct student *p1,*p2;
    int j;
    for(j=1;j<=n;j++)
    {p1=p2=(struct student *)malloc(LEN);
    &p1->num=j;
    head=NULL;
    while(p1->num!=0)
    {
        n=n+1;
        if(n==1)head=p1;
        else p2->next=p1;
        p2=p1;
        /*p1=(struct student*)malloc(LEN);
        scanf("%ld",&p1->num);
        */
    }
    }
p2->next=NULL;
return(head);
}
struct student *del(struct student *head)
{
    struct student *p1,*p2;
    int i;
    if(head==NULL){printf("\nlist null!\n");return(head);}
    p1=head;
    for(i=0;;i++)
 {
        
    /*loop:*/ p2=p1;p1=p1->next;
            
    if(i%3==0)
        {/*if(p1==head)head=p1->next;*/
        /*else*/ p2->next=p1->next;
        n=n-1;
        }
    if(p1->next==NULL)
    p1->next=head;
/*    goto loop;*/
    if(n==1)
    return(head);
 /*   break;*/
 }
}
void print(struct student *head)
{
    struct student *p;
    printf("\nNow,These %d records are:\n",n);
    p=head;
    if(head!=NULL)
    do
    {printf("%ld",p->num);
        p=p->next;
        }while(p!=NULL);
    }
void main()
{
    int n;
 struct student *head;
 printf("input  n:\n");
 scanf("%ld\n",&n);
 head =creat();
 print(head);
 printf("\nnow begin to delete number three.");
 head=del(head);
  printf("\nnow begin to show the last number.");  
  print(head);
}帮忙修正一下，谢谢了。