#include <bits/stdc++.h>
using namespace std;
vector<long long> v;
void brute(long long num) {
  v.push_back(num);
  if (num > 1000000000) return;
  brute(num * 10 + 4);
  brute(num * 10 + 7);
}
int main() {
  ios::sync_with_stdio(false);
  brute(0);
  sort(v.begin(), v.end());
  int n;
  cin >> n;
  cout << lower_bound(v.begin(), v.end(), n) - v.begin() << endl;
  return 0;
}
