import java.util.Scanner;

public class Kaibun {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int count = 0;
		long t = (long)Math.pow(10, 9) +1 , N = s.nextLong();
		s.close();
		for(long i = 1l;i * t <= N ;i++){
			String str = String.valueOf(i*t);
			StringBuffer str2 = new StringBuffer(str);
			
			if(i * t == Long.parseLong(str2.reverse().toString())){
				count++;
			}
		}
		System.out.println(count);
	}
}