class Euler27 {

    private static class Options {
        int abs_a = 999;
        int abs_b = 999;
        boolean run_checkpoints = true;
    }

    private static boolean parse_int_after_prefix(String arg, String prefix, java.util.function.IntConsumer setter) {
        if (!arg.startsWith(prefix)) {
            return false;
        }
        String tail = arg.substring(prefix.length());
        if (tail.isEmpty()) {
            return false;
        }

        int parsed = 0;
        for (int i = 0; i < tail.length(); i++) {
            char c = tail.charAt(i);
            if (c < '0' || c > '9') {
                return false;
            }
            parsed = parsed * 10 + (c - '0');
        }
        setter.accept(parsed);
        return true;
    }

    private static boolean parse_arguments(String[] args, Options options) {
        for (String arg : args) {
            if ("--skip-checkpoints".equals(arg)) {
                options.run_checkpoints = false;
                continue;
            }
            if (parse_int_after_prefix(arg, "--abs-a=", val -> options.abs_a = val)) {
                continue;
            }
            if (parse_int_after_prefix(arg, "--abs-b=", val -> options.abs_b = val)) {
                continue;
            }

            System.err.println("Unknown argument: " + arg);
            return false;
        }

        return options.abs_a >= 0 && options.abs_b >= 0;
    }

    private static boolean is_prime(long n) {
        if (n < 2) {
            return false;
        }
        if ((n & 1L) == 0L) {
            return n == 2;
        }
        for (long p = 3; p <= n / p; p += 2) {
            if (n % p == 0) {
                return false;
            }
        }
        return true;
    }

    private static int consecutive_prime_count(int a, int b) {
        int n = 0;
        while (true) {
            long value = (long)n * n + (long)a * n + b;
            if (!is_prime(value)) {
                break;
            }
            ++n;
        }
        return n;
    }

    private static int solve(int abs_a, int abs_b) {
        int best_a = 0;
        int best_b = 0;
        int best_count = -1;

        for (int a = -abs_a; a <= abs_a; ++a) {
            for (int b = -abs_b; b <= abs_b; ++b) {
                if (!is_prime(b)) {
                    continue;
                }
                int count = consecutive_prime_count(a, b);
                if (count > best_count) {
                    best_count = count;
                    best_a = a;
                    best_b = b;
                }
            }
        }

        return best_a * best_b;
    }

    private static boolean run_checkpoints() {
        if (consecutive_prime_count(1, 41) != 40) {
            System.err.println("Checkpoint failed for n^2+n+41");
            return false;
        }
        if (consecutive_prime_count(-79, 1601) != 80) {
            System.err.println("Checkpoint failed for n^2-79n+1601");
            return false;
        }
        return true;
    }

    public static void main(String[] args) {
        Options options = new Options();
        if (!parse_arguments(args, options)) {
            System.exit(1);
        }

        if (options.run_checkpoints && !run_checkpoints()) {
            System.exit(2);
        }

        System.out.println(solve(options.abs_a, options.abs_b));
    }
}