using System;

using System.Linq;

using System.Numerics;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Write binary number to be converted into decimal");

        string input = Console.ReadLine().Trim();

        if (!input.All(c => c == '0' || c == '1'))

            Console.WriteLine("Syntax error: binary value must contain 0 and 1 only");

        else {

            BigInteger result = input.Aggregate(BigInteger.Zero, (s, a) => s * 2 + a - '0');

            Console.WriteLine("binary \"" + input + "\" == " + result);

        }

    }

}