我有个链表删除节点的问题，删除节点时，程序运行终止我找不出问题在那里，找了好久找不出原因所在

源代码如下：

#include <stdio.h>
#include <stdlib.h>

#define LEN sizeof(struct student)

struct student *creat(void);
void print(struct student *head);
struct student *del(struct student *head, long num);

struct student
{
    long num;
    float score;
    struct student *next;
};

int n;

int main()
{
    struct student *head, *stu;
    long del_num;
    printf("input records:\n");
    head = creat();
    print(head);
    printf("\ninput the deleted number:");
    scanf("%ld,&del_num");
    head = del(head,del_num);
    print(head);
    return(0);
}

struct student *creat(void)
{   

    struct student *head;
    struct student *p1,*p2;
    n = 0;
    p1 = p2 = (struct student *)malloc(LEN);

    scanf("%ld,%f",&p1->num,&p1->score);
    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,%f",&p1->num,&p1->score);
    }

    p2->next = NULL;
    return(head);
}

void print(struct student *head)
{
    struct student *p;
    printf("\nNow, These %d records are:\n",n);
    p = head;
    if(head != NULL)
        do
    {
        printf("%ld \t%5.1f\n", p->num, p->score);
        p = p->next;
    } while(p != NULL);
}

struct student *del(struct student *head, long num)
{
    struct student *p1,*p2;
    if(head == NULL)
        {printf("\nlist null!\n");
         return(head);
        }
    p1 = head;
    while(num!=p1->num && p1->next!=NULL)
        {p2=p1;p1=p1->next;}
    if(num == p1->num)
        {if(p1 == head) head=p1->next;
         else p2->next = p1->next;
         printf("delete:%ld\n",num);
         n=n-1;
        }
    else printf("%ld not been found!\n", num);
    return(head);
}

主函数里面的问题，如下标记：
int main()
{
    struct student *head, *stu;
    long del_num;
    printf("input records:\n");
    head = creat();
    print(head);
    printf("\ninput the deleted number:");
    scanf("%ld",&del_num);//*********************************************,&del_num被放进了引号
    head = del(head,del_num);
    print(head);
    return(0);
}

谢谢你，你要不指出问题所在，我还真找不出来问题出在那里。