Nine Digit Magic Number

using System;
namespace NineDigitMagicNumber
{
    class Nine
    {
        static void Main()
        {
            int sum = int.Parse(Console.ReadLine());
            int diff = int.Parse(Console.ReadLine());
            int result = 0;
            for (int num1 = 111; num1 <= 777; num1++)
            {
                int num2 = num1 + diff;
                int num3 = num2 + diff;
                if ( allow(num1) && allow(num2) && allow(num3) && (num3 <= 777) &&
                    calcsum(num1) + calcsum(num2) + calcsum(num3) == sum)
                {
                    Console.WriteLine("{0}{1}{2}", num1, num2, num3);
                     result++;
                }
            }
        }


        private static object calcsum(int num)
        {
            int sum = 0;
            while ( num > 0)
            {
                sum += num % 10;
                num = num / 10;
            }
            return sum;
        }

        private static bool allow(int num)
        {
            string digits = num.ToString();
            foreach (var digit in digits )
            {
                if ( digit < '1' || digit > '7')
                {
                    return false;
                }
            }
            return true;
        }
    }
}