#include<bits/stdc++.h>
using namespace std;
int main()
{
    string n;
    cin>>n;
    int s = 0;
    int k = 1;
    for(int i = n.size()-1;i>=0;i--)
    {
        s+=(n[i]-48) * k;
        k=k*2;
    }
    cout<<s;
}
/**************************************************************
	Problem: 1290
	User: wuyichen
	Language: C++
	Result: Accepted
	Time:14 ms
	Memory:2076 kb
****************************************************************/