求助第四个点wa

#include<stdio.h>
int main()
{
    int n,i,j;
    char a[55];
    scanf("%d\n",&n);
    scanf("%s",a);
    if (n>=26)
        j=n%26;
    else
        j=n;
    for (i=0;a[i]!='\0';i++)
    {
        a[i]=a[i]+j;
        if (a[i]>'z')
            a[i]=a[i]-26;
    }
    printf("%s",a);
    return 0;
}