6、求一个数的偶数位的乘积（个位、百位、万位、百万位 等等 注：不允许操作字符串）。

class Program
    {
        static void Main(string[] args)
        {
          

            #region 6、求一个数的偶数位的乘积（个位、百位、万位、百万位 等等 注：不允许操作字符串）。
            //                               个位、十位、百位、千位、万位、十万位、百万位

            float num = 0;
            while (true)
            {
                Console.WriteLine("请输入任意一个4位数以上的正整数：");
                num = float.Parse(Console.ReadLine());
                if (num >= 1000)
                {
                    break;
                }
            }
            if (1000 <= num && num < 100000)
            {
                int shiwei = GetNum(num, 0);
                int qianwei = GetNum(num, 1);
                Console.WriteLine("结果是：{0}", shiwei * qianwei);
            }
            else if (100000 <= num && num < 10000000)
            {
                int shiwei = GetNum(num, 0);
                int qianwei = GetNum(num, 1);
                int shiwanwei = GetNum(num, 2);
                Console.WriteLine("结果是：{0}", shiwei * qianwei * shiwanwei);
            }
            else
            {
                int shiwei = GetNum(num, 0);
                int qianwei = GetNum(num, 1);
                int shiwanwei = GetNum(num, 2);
                int qianwanwei = GetNum(num, 3);
                Console.WriteLine("结果是：{0}", shiwei * qianwei * shiwanwei * qianwanwei);
            }






            Console.ReadLine();
            #endregion


        }

        public static int GetNum(float num, int i)
        {
            int result = 0;
            int wei = 1;

            if (i == 0)
            {
                wei = 100;
            }
            if (i == 1)
            {
                wei = 10000;
            }
            if (i == 2)
            {
                wei = 1000000;
            }
            if (i == 3)
            {
                wei = 100000000;
            }


            float c = num / wei;
            int a = (int)(c);
            float b = c - a;
            result = (int)(b * 10);
            return result;
        }
    }