题解 | #自守数#

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
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int num = in.nextInt();
            int count = 1;
            int countBit = 10;
            int temp;

            for(int i = 1; i <= num; i++){
                temp = i;
                countBit = 10;
                while(temp / 10 != 0){
                    countBit *= 10;
                    temp /= 10;
                }
                if((i * i - i) % countBit == 0 ){

                    count++;
                }
            }
            System.out.println(count);
        }
    }
}