#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: fzy001
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2076 kb
****************************************************************/