#include <bits/stdc++.h>

using namespace std;

int todecimal(string s) {
    long long deci = 0, power = 1;
    for (int i = s.size() - 1; i >= 0; i--) {
        if (s[i] == '1') deci += power;
        power *= 2;
    }
    return deci;
}

int main()
{
    string s;
    cin >> s;   
    cout << todecimal(s);
    return 0;
}