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 <bits/stdc++.h>

using namespace std;

typedef long long ll;

const long long MOD = 1e9;

vector<string> num;

void dfs(int n, string s, int k) {
  if (n == 0) {
    if (s.size() > 0 && k == 7) num.push_back(s);
    return;
  }
  dfs(n - 1, s + "7", k | (1));
  dfs(n - 1, s + "5", k | (2));
  dfs(n - 1, s + "3", k | (4));
}

int main() {
  ll N;
  cin >> N;
  for (int i = 3; i <= 10; ++i) dfs(i, "", 0);
  int res = 0;
  for (auto i : num) if (stoll(i) <= N) res++;
  cout << res << endl;
}