#include<bits/stdc++.h>
using namespace std;
int main(){
string s;
cin>>s;
int c=0,t=1;
for(int i=s.size()-1;i>=0;i--){
    c=c+(s[i]-48)*t;
    t=t*2;
}
cout<<c;
    return 0;
}
/**************************************************************
	Problem: 1290
	User: linyuhang
	Language: C++
	Result: Accepted
	Time:15 ms
	Memory:2076 kb
****************************************************************/