using System;

class BinaryToDecimalNumber
{
    static void Main()
    {
        string binary = Console.ReadLine();
        char[] arr = binary.ToCharArray();
        long sum = 0;
        long bit = 0;
        for (int i = 0; i < arr.Length; i++)
        {


            bit = Convert.ToInt64(arr[i]) - 48;
            sum += bit * (long)(Math.Pow(2, (arr.Length - (i + 1))));
        }
        Console.WriteLine(sum);
    }
}