题解 | #幸运数字7#

import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int sum = 0;
        for(int i = 1; i <= n; i++){
           if(i % 7 == 0){
               sum += i;
           }
        }
        System.out.println(sum);
    }    
}