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;
vector<ll> c357num;

void dfs(string s, int digit) {
	if (3 <= digit) {
		bool exist3 = false;
		bool exist5 = false;
		bool exist7 = false;
		for (int i = 0; i < s.size(); i++) {
			if (s[i] == '3') exist3 = true;
			if (s[i] == '5') exist5 = true;
			if (s[i] == '7') exist7 = true;
		}
		if(exist3 && exist5 && exist7) c357num.push_back(stoll(s));
	}
	if (digit == 9) {
		return;
	}
	digit++;
	for (int i = 0; i < 3; i++) {

		if (i == 0) {
			s += "3";
			dfs(s, digit);
			s.pop_back();
		}
		else if (i == 1) {
			s += "5";
			dfs(s, digit);
			s.pop_back();

		}
		else { // i == 2
			s += "7";
			dfs(s, digit);
			s.pop_back();
		}

	}
}

int main() {

	ll n; cin >> n;
	if (n <= 356) {
		cout << 0 << endl;
		return 0;
	}
	string s = "";
	int d = 0;
	dfs(s, d);
	sort(c357num.begin(), c357num.end());
	ll ans = 0;
	for (int i = 0; i < c357num.size(); i++) {
		if (c357num[i] <= n) ans++;
		else break;
	}
	cout << ans << endl;
	return 0;
}