Problem:
Score : 300 points

Problem Statement

You are given an integer N. Among the integers between 1 and N (inclusive), how many Shichi-Go-San numbers (literally "Seven-Five-Three numbers") are there?

Here, a Shichi-Go-San number is a positive integer that satisfies the following condition:

When the number is written in base ten, each of the digits 7, 5 and 3 appears at least once, and the other digits never appear.

Constraints

1 \leq N < 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of the Shichi-Go-San numbers between 1 and N (inclusive).

Sample Input 1

575

Sample Output 1

4

There are four Shichi-Go-San numbers not greater than 575: 357, 375, 537 and 573.

Sample Input 2

3600

Sample Output 2

13

There are 13 Shichi-Go-San numbers not greater than 3600: the above four numbers, 735, 753, 3357, 3375, 3537, 3557, 3573, 3575 and 3577.

Sample Input 3

999999999

Sample Output 3

26484

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <algorithm>
#include <iostream>

using namespace std;

int dfs(string tmp, int size, int num) {
  // cout << tmp << endl;
  if (tmp.size() == size) {
    bool has3 = false, has5 = false, has7 = false;
    for (int i = 0; i < tmp.size(); i++) {
      if (tmp[i] == '3') {
        has3 = true;
      } else if (tmp[i] == '5') {
        has5 = true;
      } else if (tmp[i] == '7') {
        has7 = true;
      } else {
        has3 = false;
        break;
      }
    }
    if (has3 && has5 && has7 && stoi(tmp) <= num)
      return 1;
    else
      return 0;
  }
  int ret = 0;
  string number[] = {"3", "5", "7"};
  for (int i = 0; i < 3; i++) {
    ret += dfs(tmp + number[i], size, num);
  }

  return ret;
}

int main() {
  int ans = 0;
  string n;
  cin >> n;
  for (int i = 3; i <= n.size(); i++) {
    // cout << i << endl;
    ans += dfs("", i, stoi(n));
  }
  cout << ans << endl;
  return 0;
}