#include<bits/stdc++.h>
using namespace std;
int main(){
    string s;
    int c=0;
    int t=1;
    cin>>s;
    int a[1000];
    for(int i=0;i<s.size();i++){
        a[s.size()-1-i]=s[i]-'0';
    }
    for(int i=0;i<s.size();i++){
        c=c+a[i]*t;
        t=t*2;
    } 
    cout<<c;
    return 0;   
}
/**************************************************************
	Problem: 1290
	User: jiangyuanfeng
	Language: C++
	Result: Accepted
	Time:20 ms
	Memory:2076 kb
****************************************************************/