#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: chenlingxuan
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2076 kb
****************************************************************/