题解 | #自守数#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int count=0;
        for (int i = 0; i <= n; i++) {
            String s1 = String.valueOf(i);
            String s2 = String.valueOf(i * i);
            if (s1.equals(s2.substring(s2.length()-s1.length(),s2.length()))){
                count++;
            }
        }
        System.out.println(count);
    }
}