#include<bits/stdc++.h> using namespace std; int main (){ int sum=0,sum1=1; string n; cin>>n; int i=n.size()-1; while(i!=-1){ for(int j=0;j<n.size()-1-i;j++){ sum1=sum1*2; } sum+=(n[i]-48)*sum1; i--; sum1=1; } cout<<sum; return 0; }