Wrong Answer
代码
#include <stdio.h>
#include <ctype.h>
#define N 5
#define KEY 4
int
main(void)
{
    char str[N+1];
    scanf("%s", str);
    for (int i=0; i < N; i++)
    {
        if (!isupper(str[i]))
            str[i] = (str[i] + KEY - 'a' ) % 26 + 'a';
        else if (isupper(str[i]))
            str[i] = (str[i] + KEY - 'A') % 26 + 'A';
    }
    printf("%s", str);
    return 0;
}