#include<bits/stdc++.h>
using namespace std;
int main(){
    string n;
    long long k=0,t=1;
    cin>>n;
    for(int i=n.size()-1;i>=0;i--){
        k=k+(n[i]-48)*t;
        t=t*2;
    }
    cout<<k;
    return 0;
}
/**************************************************************
	Problem: 1290
	User: hongjiaming
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2076 kb
****************************************************************/