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