#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
	cin>>s;
	int c=0,t=1;
	for(int i=s;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: Compile Error
****************************************************************/