using System;

​

public class Program

{

    public static void Main()

    {

        double decimalResult = 0;

        int binary = 101010101;

        char[] chars = binary.ToString().ToCharArray(); 

        Array.Reverse(chars);

        for (int i = 0; i < chars.Length; i++)

        {

            decimalResult += double.Parse(chars[i].ToString()) * Math.Pow(2, int.Parse((i.ToString())));

        }

​

        Console.WriteLine(decimalResult);

    }

}