private static long Ylee(long N)
        {
            long count = 0; // verifiy valid (n,k) as sigma(n+k) - sigma(n) = sigma(k) + n*k

            Func<long, long> sumOfNumbersUpto = delegate (long k) { return k * (k + 1) / 2; };

            for (Int64 i = Convert.ToInt64(Math.Sqrt(2 * N)); i > 1; i--)

                if ((N - sumOfNumbersUpto(i)) % i == 0) count++;

            return count;
        }