#include<bits/stdc++.h>
using namespace std;
int main(){
	string n;
	int 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: xuanhua
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2076 kb
****************************************************************/