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