import java.util.*;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
while(scanner.hasNext()){
int num = scanner.nextInt();
List<integer> list = new ArrayList(10);
String temp = "";
for (int i = 0; i <= num; i++) {
temp = String.valueOf(i * i);
if (temp.endsWith(String.valueOf(i))) {
list.add(i);
}
}
System.out.println(list.size());
}
}
}</integer>