C语言爆零，求助

#include <stdio.h>
int main(void)
{

    int n;
    char ch;
    scanf("%d", &n);
    getchar();
    while ((ch = getchar()) <= 'z' && ch >= 'a')
    {
        ch = (ch - 'a' + n) % 26 + 'a';
        printf("%c",&ch);
    }
    return 0;
}