题解 | #自守数#

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.text.DateFormat;
import java.text.DecimalFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;
import java.util.*;
import java.util.stream.IntStream;
import java.util.stream.Stream;

import static java.util.Arrays.*;
import static java.util.stream.Stream.*;


public class Main {
    public static void main(String[] args) throws IOException {

        testTh();
    }

    private static void testTh() throws IOException {
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        String str;
        while ((str = bf.readLine()) != null) {
            int parseInt = Integer.parseInt(str);
            int count = 0;
            for (int i = 0; i <= parseInt; i++) {
                Integer pow = (int) (Math.pow(i, 2));
                String s1 = i + "";
                String s = pow + "";
                if (s1.equals(s.substring(s.length() - s1.length()))) {
                    count++;
                }

            }
            System.out.println(count);

        }

    }




}