题解 | #矩阵乘法计算量估算#

import java.util.*;

public class Main {

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    while (in.hasNextLine()) {
        int num = Integer.parseInt(in.nextLine());
        System.out.println(getNum(num));
    }
}

public static int getNum(int a){
    int count = 0;
    for(int i=0;i<= a;i++){
       int length = String.valueOf(i).length();
       if(Math.pow(i,2) % Math.pow(10,length) == i){
           count++;
       }
    }
    return count;
}

}