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: Wrong Answer)


#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i, n) for(int i = 0; i < (int)(n); i++)

ll N;
ll cnt = 0;
int length;

int hand[3] = {3, 5, 7};

void dfs(int n, ll ans) {
    // cout << ans << endl;

    if(333 <= ans && ans < N) {
        bool f_3 = false;
        bool f_5 = false;
        bool f_7 = false;
        if(to_string(ans).find("3") != std::string::npos) f_3 = true;
        if(to_string(ans).find("5") != std::string::npos) f_5 = true;
        if(to_string(ans).find("7") != std::string::npos) f_7 = true;
        if((f_3 + f_5 + f_7) == 3) cnt++;
    }
    if(n == length) {
        return;
    }
    for(int i = 0; i < 3; i++) {
        dfs(n + 1, ans + hand[i] * pow(10, n));
    }
}
int main() {
    vector<int> flags(3, 0);
    cin >> N;

    // while(N / 10) {
    //     nums.push_back(N % 10);
    //     N /= 10;
    // }
    // nums.push_back(N % 10);
    length = to_string(N).size();
    dfs(0, 0);
    cout << cnt << endl;
    return 0;
}