import java.util.*;
public class HJ99 {
public HJ99(){
}
public static void main(String[] args){
HJ99 solution = new HJ99();
Scanner in = new Scanner(System.in);
while(in.hasNext()){
int num = in.nextInt();
int res = solution.count(num);
System.out.println(res);
}
}
private int count(int num) {
int count=0;
while(num>=0) {
int m = num*num;
int size = String.valueOf(num).length();
int size1 = String.valueOf(m).length();
String actnum = String.valueOf(m).substring(size1-size);
if(actnum.equals(String.valueOf(num))){
count++;
num--;
}else {
num--;
}
}
return count;
}
}
public class HJ99 {
public HJ99(){
}
public static void main(String[] args){
HJ99 solution = new HJ99();
Scanner in = new Scanner(System.in);
while(in.hasNext()){
int num = in.nextInt();
int res = solution.count(num);
System.out.println(res);
}
}
private int count(int num) {
int count=0;
while(num>=0) {
int m = num*num;
int size = String.valueOf(num).length();
int size1 = String.valueOf(m).length();
String actnum = String.valueOf(m).substring(size1-size);
if(actnum.equals(String.valueOf(num))){
count++;
num--;
}else {
num--;
}
}
return count;
}
}