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)

// C.

#include <iostream>
#include <sstream>
#include <algorithm>
#include <vector>
#include <cstring>

using namespace std;

int main(int argc, char *argv[]) {
	long long n, len = 0, ans = 0;
	cin >> n;
	char d[16] = {};
	while (true) {
		int pos = 12;
		while (true) {
			if (!d[pos]) {
				++len;
				d[pos] = '3';
				break;
			} else if (d[pos] == '3') {
				d[pos] = '5';
				break;
			} else if (d[pos] == '5') {
				d[pos] = '7';
				break;
			} else if (d[pos] == '7') {
				d[pos] = '3';
				--pos;
			}
		}
		if (atoll(d + 13 - len) > n) {
			break;
		}
		int f = 0;
		for (int i = 0; i < len; ++i) {
			if (d[12 - i] == '3') f |= 1;
			else if (d[12 - i] == '5') f |= 2;
			else f |= 4;
		}
		ans += f == 7;
	}
	cout << ans << endl;
	return 0;
}