int string_prefix(const char * s, const char * p) {
    while (*p != 0) {
	if (*p != *s)
	    return 0;
	++p;
	++s;
    }
    return 1;
}

int contains_str(const char * s, const char * x) {
    if (*x == 0)
	return 1;
    
    while (*s != 0) {
	if (string_prefix(s, x))
	    return 1;
	++s;
    }
    return 0;
}