题解 | #完全数计算#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        int res = 0;
        for (int i = 1; i <= n; i++) {
            if (isPN(i)) {
                res++;
            }
        }
        System.out.println(res);
    }

    private static boolean isPN(int num) {
        List<Integer> list = new ArrayList<>();
        for (int i = 1; i < num; i++) {
            if (num % i == 0) list.add(i);
        }
        int count = 0;
        for (Integer i : list) {
            count += i;
        }
        if (count == num) return true;
        return false;
    }
}