uint64_t kstrncmp(char *str1, char *str2, uint64_t len){
    uint64_t index_str = 0;
    uint64_t different_char = 0;
    while (index_str < len) {
        if (str1[index_str] != str2[index_str]) {
            different_char++;
        }
        index_str++;
    }
    return different_char;
}