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;

vector<int> tfs = {3, 5, 7};
int ans = 0;

void dfs(int n, int m, int cur, vector<int> used) {
	if (m <= n && used.at(0) > 0 && used.at(1) > 0 && used.at(2) > 0) ans++;
	if (cur < 9) {
		int p = 1;
		for (int i = 0; i < cur; i++) {
			p *= 10;
		}
		for (int i = 0; i < 3; i++) {
			used.at(i)++;
			dfs(n, m + tfs.at(i) * p, cur + 1, used);
			used.at(i)--;
		}
	}else return;
}

int main() {
	int n; cin >> n;
	vector<int> used(3, 0);
	dfs(n, 0, 0, used);
	cout << ans << endl;
}