#include <iostream>
#include <cmath>
#include <string>


using namespace std;
using ll = long long;

ll decimalToBinary(ll n) {
    if (n == 0) return 0;

    string result = "";

    while (n > 0) {
        result = to_string(n % 2) + result; 
        n /= 2;
    }

    return stoll(result);
}

int main()
{
    ll num, i=0, db=0, newnum;
    cin >> num;
    while (num>=(3*decimalToBinary(i))) {
        db++;i++;
    }
    cout << db;
}