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