static void Main(string[] args)
        {
            string numString = "123045";
            long num = GetNum(numString);
            Console.WriteLine(num);
        }

        private static long[] ten = new long[] { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000 };

        public static long GetNum(string NumString)
        {
            char[] NumArray = NumString.ToCharArray();
            long Num = 0L;
            for (int i = NumArray.Length - 1, j = 0; i >= 0; i--, j++)
            {
                Num += (NumArray[i] - '0') * ten[j];
            }
            return Num;
        }