int printf(const char* format, ...);

int strcmp(const char* s1, const char* s2) {
    while (*s1 && *s2 && *s1 == *s2) {
        s1++;
        s2++;
    }
    return *s1 - *s2;
}

int main() {
    const char* s1 = "helloworld";
    const char* s2 = "world";
    printf("%d\n", strcmp(s1, s2));
    printf("%d\n", strcmp(s1 + 5, s2));
}