using System;

class ConvertBinToDec
{
    static int Power(int number, int pow)
    {
        if (pow == 0)
        {
            return 1;
        }
        for (int i = 0; i < pow - 1; i++)
        {
            number *= 2;
        }
        return number;
    }

    static void Main()
    {
        string number = Console.ReadLine();
        int temp;
        int pow = 0;
        int result = 0;
        for (int i = number.Length - 1; i >= 0; i--)
        {
            int some = Convert.ToInt32(number[i].ToString());
            temp = some * Power(2, pow);
            result += temp;
            pow++;
        }
        Console.WriteLine(result);
    }
}