include <stdio.h>

是因为linus系统换行符不是\n的缘故吗

int main() {

long long n, m;
scanf("%lld", &n);
getchar();
n = n % 26;
while ((m = getchar()) != '\n')
{
    if (m + n > 'z')
        n -= 26;
    putchar(m + n);
}
return 0;

}