public class Advent4 {
    public static boolean check(byte[] b, boolean part1) {
        return (b[0] | b[1] | (part1 ? (b[2] >> 4 & 0xf) : b[2])) == 0;
    }

    public static void main(String[] args) throws Exception {

        MessageDigest md = MessageDigest.getInstance("MD5");
        String test = "ckczppom";
        int pad = 1;
        long time = System.currentTimeMillis();
        while (pad < Integer.MAX_VALUE) {
            byte[] md5 = md.digest((test + pad++).getBytes());
            if (check(md5, true)) break; // true for part1, false for part2
        }
        System.out.println("Answer: " + (pad - 1));
        System.out.println("Time: " + (System.currentTimeMillis() - time) + "ms");
    }
}