题解 | #完全数计算#

import java.util.Scanner;

// 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);
        // 注意 hasNext 和 hasNextLine 的区别
        int n = in.nextInt();
        int num = 0;
        for (int i = 2; i < n + 1; i++) {
            int k = (int)Math.sqrt(i);

            int sum = 1;
            for (int j = 2; j < k + 1; j++) {
                if (i % j == 0) {
                    sum = sum + j + i / j;
                }
            }

            if (sum == i) {
                num++;
            }
        }

        System.out.println(num);
    }
}