using System;
class BinaryToDecimalNumber
{
    static void Main()
    {
        Console.Write("Enter the binary representation of a number: ");
        string input = Console.ReadLine();
        char[] inputToArray = input.ToCharArray();
        int degree = input.Length - 1;
        long result = 0;

        for (int i = 0; degree >= 0; i++, degree--)
        {
            result += ((long)Char.GetNumericValue(inputToArray[i]) * (long)Math.Pow(2, degree));
        }
        Console.WriteLine(result);
    }
}