1,11,111

//1*11*111*1111*11111+?
            int q = 0;
            long sum = 0;
            for (int i = 0; i < 10; i++)
            {
                q = q * 10 + 1;
                sum = sum + q;
                //an=(10^n -1)/9
            }
            Console.WriteLine(sum);