import java.util.*;
public class Main {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner sc =new Scanner(System.in);
int n=sc.nextInt();
String s=n+"";
String[] arr=s.split("");
int sum=0;
for(int i=0;i<arr.length;i++){
int p=Integer.parseInt(arr[i]);
if(p==0) continue;
if(p==1){
sum=sum+(int)Math.pow(2, arr.length-i-1);
}
}
System.out.println(sum);
}
}