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<iostream>
#include<set>
#include<algorithm>
using namespace std;

int n;
set<string> se;

bool check(string s){
    int ret = 0;
    for(char c : s){
        if(c == '3')    ret |= 1;
        if(c == '5')    ret |= 2;
        if(c == '7')    ret |= 4;
    }
    return ret == 7;
}

void dfs(string s){
    if(se.count(s)) return;
    if(stoi(s) > n) return;
    if(check(s) && stoi(s) <= n){
        se.insert(s);
    }
    if(s.length() == 9) return;
    dfs(s+"3");
    dfs(s+"5");
    dfs(s+"7");
}

int main(){
    cin >> n;
    
    dfs("3");
    dfs("5");
    dfs("7");

    cout << se.size() << endl;

    return 0;
}