大佬们帮帮我吧

#include<stdio.h>
#include<stdlib.h>
struct zimu
{
    char c;
    struct zimu *next;
};
int main(void)
{
    int i,n,j;
    scanf("%d", &n);
    getchar();
    char c0 = 'a';
    struct zimu *p1;
    struct zimu *p2;
    struct zimu *head;
    p1 = (struct zimu *)malloc(sizeof(struct zimu));
    head = p1;
    for (i = 1;i <= 26;i++)
    {
        p1->c = c0;
        c0++;
        if (i == 26)
        {
            p1->next = head;
            break;
        }
        p2 = p1;
        p1 = (struct zimu*)malloc(sizeof(struct zimu));
        p2->next = p1;
    }
    char a[50];
    for (i = 0;i <= 49;i++)a[i] = '\0';
    c0 = getchar();
    for (i = 0;c0 != '\n';i++)
    {
        a[i] = c0;
        c0 = getchar();
    }
    struct zimu *p;
    for (i = 0;a[i] != '\0';i++)
    {
        for (p = head;p->c != a[i];p = p->next);
        for (j = 1;j <= n;j++)p = p->next;
        a[i] = p->c;
    }
    for (i = 0;a[i] != '\0';i++)printf("%c", a[i]);
    return 0;
}

这个为什么全部WA？