题解 | #挑7#

import java.util.*;

// 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 in = new Scanner(System.in);
        int a = in.nextInt();
        System.out.println(cal(a));
    }

    private static int cal(int n){

        HashSet<Integer> set = new HashSet<>();

        for(int i = 1; i <= n; i++){
            if(i % 7 == 0){
                set.add(i);
            }
            else{
                String s = String.valueOf(i);
                if(s.contains("7")){
                    set.add(i);
                }
            }
        }

        return set.size();
    }
}