#include<bits/stdc++.h>
using namespace std;
int main()
{
	string s;
	cin>>s;
	int t=1;
	int r=0;
	for(int i=s.size()-1;i>=0;i--){
		r=r+(s[i]-'0')*t;
		t=t*2;
	}
	cout<<r;
}

/**************************************************************
	Problem: 1290
	User: zhuangsongyu
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2076 kb
****************************************************************/