#include<bits/stdc++.h> using namespace std; string a; int main() { cin>>a; int n = a.size(); int x = 0,j = 0; for (int i = n - 1;i >= 0;i--){ if (a[i] == '1'){ x += 1 * pow(2,j); } j++; } cout<<x; return 0; }