题解 | #挑7#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner fzhinput = new Scanner(System.in);
        int n = fzhinput.nextInt();
        int num=0;
        for(int i=1;i<=n;i++){
            String zf = Integer.toString(i);
            if(i%7==0){
                num++;
                continue;
            }
            for(int j=0;j<zf.length();j++){
                if(zf.charAt(j)=='7'){
                    num++;
                    break;
                }
            }
        }
        System.out.print(num);
    }
}