为什么链表会无限循环输出？？

Question

#include<stdio.h>
#include<stdlib.h>//含malloc.h
#define LEN sizeof( Faction)
//一元多项式结构体
typedef struct Faction{
    int coefficient;//系数
    int exponent;//指数
    struct Faction *next;
}Faction;
//创建链表
Faction *creat() {
    Faction *head, *p1, *p2;
    head = NULL;
    p1 = p2 = (Faction*)malloc(LEN);
    scanf("%d %d", &(p1->coefficient), &(p1->exponent));
    p1->next = NULL;
    while(p1->coefficient != -1 || p1->exponent != -1) {
        if(head == NULL)
            head = p1;
        else
            p2->next = p1;
        p2 = p1;
        p1 = (Faction*)malloc(LEN);
        scanf("%d %d", &(p1->coefficient), &(p1->exponent));//此处可以顺便统数据个数
    }
    p2->next = NULL;
    return head;
}
//输出链表
void Print(Faction *head) {
    Faction *p;
    p = head;
    while(p != NULL) {
        printf("%d %d", p->coefficient, p->exponent);//空格就是\
        p = p->next;
    }
}
//计算降幂
void Calculate(Faction *head) {
    Faction *p;
    p = head;
    while(p != NULL) {
        p->coefficient = p->coefficient * p->exponent;
        p->exponent -= p->exponent;
        if(p->coefficient == 0)
            break;
        p = p->next;
    }
}
//
int main() {
    Faction *head;
    head = NULL;
    head = creat();
    Print(head);
    return 0;
}

Answer 1

if(head == NULL)
head = p1;
else
p2->next = p1;
p2 = p1;
这里第二次进来时， p2->next = p1，然后 p2 = p1。这就死循环了