题解 | #自守数#

import java.util.*;
import java.io.*;

public class Main{
    public static void main(String [] args) throws Exception{
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        int num = Integer.parseInt(bf.readLine());
        int count = 0;
        for(int i = 0; i<=num; i++){
            String a = String.valueOf(i);
            String x = String.valueOf(i*i);
            if(a.equals(x.substring(x.length()-a.length()))){
                count++;
            }
        }
        System.out.print(count);
    }
}