public class Euler131 {
    static boolean isPrime(int n) {
        if (n < 2)
            return false;
        if (n % 2 == 0)
            return n == 2;
        for (int p = 3; (long) p * p <= n; p += 2)
            if (n % p == 0)
                return false;
        return true;
    }

    public static void main(String[] args) {
        int limit = 1000000, count = 0;
        for (int a = 1;; a++) {
            int p = 3 * a * a + 3 * a + 1;
            if (p >= limit)
                break;
            if (isPrime(p))
                count++;
        }
        System.out.println(count);
    }
}