#include<bits/stdc++.h>
using namespace std;
int main(){
	string s;
	int k=0,t=1;
	cin>>n;
	for(int i=s.size()-1;i>=0;i--){
		k=k+(n[i]-48)*t;
		t*=2;
	}		
	cout<<k;														
	return 0;
} 
/**************************************************************
	Problem: 1290
	User: houlingqi2
	Language: C++
	Result: Compile Error
****************************************************************/