看了几遍才知道啥意思。。例如：25^2 = 625，尾数25

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();

        int count = 0;
        for (int i = 0; i <= n; i++) {
            String naturalNumber = String.valueOf(i);
            // 自然数的平方
            String powString = String.valueOf((int) Math.pow(i, 2));
            // 切割尾数
            String substring = powString.substring(powString.length() -
                                                   naturalNumber.length());
            if (substring.equals(naturalNumber)) {
                count++;
            }
        }
        System.out.println(count);
    }
}