import java.util.Scanner;

public class Kaibun {
	static int count;

	public static void main(String[] args) throws InterruptedException {
		Scanner s = new Scanner(System.in);
		long t = (long)Math.pow(10, 9) +1 , N = s.nextLong();
		s.close();
		
		for(int i = 1;i <= (int)(N/t);i++){
			String str = Integer.toString(i);
			StringBuilder str2 = new StringBuilder(str);
			if(str.contentEquals(str2.reverse())){
				count++;
			}
		}
		System.out.println(count);
	}
}