#include <bits/stdc++.h>
using namespace std;
int main(){
    string s;
    long long k=1,s1=0;
    cin>>s;
    for (int i=s.size()-1;i>=0;i--)
    {
    	if (s[i]=='1') s1=s1+k;
    	k=k*2;
	}
    cout<<s1<<endl;
}
 

/**************************************************************
	Problem: 1290
	User: admin
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2076 kb
****************************************************************/