题解 | #挑7#

import java.util.Scanner;
import java.util.*;
import java.util.regex.Pattern;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int s1 = input.nextInt();
        HashSet<Integer> hashSet = new HashSet<>();
        for (int i = 1; i <= s1; i++) {
            String s2 = String.valueOf(i);
            Pattern p1 = Pattern.compile("7+");
            if (i % 7 == 0) {
                hashSet.add(i);
            } else if (p1.matcher(s2).find()) {
                hashSet.add(i);
            }


        }
        System.out.println(hashSet.size());
    }
}