One beautiful July morning a terrible thing happened in Mainframe: a mean virus Megabyte somehow got access to the memory of his not less mean sister Hexadecimal. He loaded there a huge amount of n different natural numbers from 1 to n to obtain total control over her energy.

But his plan failed. The reason for this was very simple: Hexadecimal didn't perceive any information, apart from numbers written in binary format. This means that if a number in a decimal representation contained characters apart from 0 and 1, it was not stored in the memory. Now Megabyte wants to know, how many numbers were loaded successfully.

Input

Input data contains the only number n (1 ≤ n ≤ 109).

Output

Output the only number — answer to the problem.

Examples

Input

10


Output

2

Note

For n = 10 the answer includes numbers 1 and 10.
#include <bits/stdc++.h>
using namespace std;
long long n, sum, ans;
string number_to_string(int x) {
  if (!x) return "0";
  string s = "";
  while (x) {
    s.push_back(x % 10 + '0');
    x /= 10;
  }
  reverse(s.begin(), s.end());
  return s;
}
int funt(int sum) {
  string s = number_to_string(sum);
  for (int i = 0; i < s.size(); i++) {
    bool sure = false;
    while (s[i] == '2') {
      sure = true;
      for (int j = i; j < s.size(); j++) {
        s[i] = '0';
      }
      i--;
      if (i == -1) {
        string s1 = "1";
        s1.append(s);
        s = s1;
        i = 0;
        break;
      }
      s[i] = (char)((int)s[i] + 1);
    }
    if (sure) break;
  }
  int b = atoi(s.c_str());
  return b;
}
int main() {
  cin >> n;
  while (sum <= n) {
    sum++;
    sum = funt(sum);
    if (sum <= n) ans++;
  }
  cout << ans;
  return 0;
}
