import java.util.Scanner;
// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
scanner.useDelimiter("\n");
while (scanner.hasNextInt()) {
int i = scanner.nextInt();
int res = 0;
for (int j = 0; j <= i; j++) {
String ping = j * j + "";
String original = j + "";
if (ping.endsWith(original)) {
res++;
}
}
System.out.println(res);
}
}
}



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