#include<iostream>
using namespace std;

int main()
{

     char digit;
     int num = 0;
     cin >> digit;
    
      while ( digit =='0' || digit == '1')
     {
           num = 2*num + digit - '0';
           cin >> digit;
           
     }
           
     cout << num <<endl;

    system("pause");
    return 0;
}